JP2000114107A - Nonaqueous electrolytic solution for electric double layer capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a nonaqueous electrolytic solution, which can make an electric double layer capacitor to highly reliably work for a long period, by preparing the solution by dissolving a fluorine-containing compound in a nonaqueous solvent so that the hydrogen fluorine content of the solution becomes a specific value or smaller. SOLUTION: A nonaqueous electrolytic solution for electric double layer capacitor is set to contain 30 ppm or lower hydrogen fluoride. A quaternary ammonium salt or quaternary phosphonium salt expressed by Q+X- (where, Q+ represents a quaternary ammonium group or quaternary phosphonium group and X- represents a counter ion selected from among PF6, BF4, AsF6, N(CF3 SO3)2, C(CF3SO3)3, SbF6, and RfSO3 (where, Rf represents a 1-8C fluoroalkyl group)) is used as a fluorine-containing compound which is used for the solution as an electrolyte. The quaternary ammonium group is prepared by changing a tertiary amine to the quaternary ammonium group with an alkyl group, etc. In addition, the quaternary phosphonium group is prepared by bonding a 1-20C hydrocarbon group, such as the alkyl group, etc., to the central phosphonium atom.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte containing a fluorine-containing compound as an electrolyte, which is used for an electric double layer capacitor. More specifically, the present invention relates to a non-aqueous electrolyte for an electric double layer capacitor in which hydrogen fluoride contained as an impurity in the non-aqueous electrolyte is reduced to an extremely small amount.

[0002]

2. Description of the Related Art An electric double layer capacitor using a non-aqueous electrolytic solution has a characteristic that the withstand voltage can be increased, so that the energy density can be higher than that of an electric double layer capacitor using an aqueous electrolytic solution. In particular, those using a non-aqueous electrolyte are suitable for electric double layer capacitors for power applications having a capacitance of 50 F or more, which have recently attracted attention.

As a non-aqueous electrolyte used for an electric double-layer capacitor, a solution obtained by dissolving a quaternary ammonium borofluoride in propylene carbonate or the like (Tanahashi et al., Electrochemistry, Vol. 56, p. 892, 1988) And borofluorinated quaternary phosphonium salts dissolved in propylene carbonate or the like (Hiratsuka et al., Electrochemistry, 59, 209,
1991), one using an asymmetric quaternary ammonium salt (Japanese Patent Publication No. 3-58526), one using an asymmetric quaternary ammonium salt and a pyridinium salt dissolved in an organic solvent (Japanese Patent Publication No. 2-57694). Gazettes) are known.

[0004]

However, electric double layer capacitors using these non-aqueous electrolytes have a problem that they lack long-term reliability. According to the study of the present inventors, this is due to the presence of hydrogen fluoride in the electrolytic solution. That is, the quaternary ammonium borofluoride and the quaternary phosphonium borofluoride used as the electrolyte usually contain a small amount of hydrogen fluoride as an impurity. The electrolytic solution obtained by dissolving a salt or the like in a non-aqueous solvent naturally contains hydrogen fluoride. Further, impurities contained in these quaternary ammonium salts and quaternary phosphonium salts may react with a small amount of water in a non-aqueous solvent to generate hydrogen fluoride.

Although the amount of hydrogen fluoride in the non-aqueous electrolytic solution is very small, it deteriorates the electrolytic solution itself for a long period of time to increase the internal resistance, or the current collector or metal of the electrode of the electric double layer capacitor. Corrosion of the inner surface of the case. These obstacles caused by hydrogen fluoride in the electrolytic solution are one of the main causes of the poor long-term reliability of conventional electric double layer capacitors using a non-aqueous electrolytic solution. Accordingly, an object of the present invention is to provide a non-aqueous electrolyte which provides an electric double layer capacitor having long-term reliability.

[0006]

The non-aqueous electrolyte for an electric double layer capacitor according to the present invention has a compound containing fluorine dissolved in a non-aqueous solvent as an electrolyte and has a hydrogen fluoride content of 30 ppm or less. It is characterized by being.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The content of hydrogen fluoride in the non-aqueous electrolyte according to the present invention is 30.
ppm or less. When hydrogen fluoride exceeding 30 ppm is contained, the metal part of the electric double layer capacitor manufactured using the same is corroded, causing problems such as deterioration of capacity and increase in internal resistance. . Hydrogen fluoride content in non-aqueous electrolyte is 20p
pm or less, particularly preferably 10 ppm or less. In order to produce an electrolytic solution in which the content of hydrogen fluoride is reduced to such a small amount, for example, a compound containing substantially anhydrous fluorine, which has been sufficiently purified in advance by recrystallization or the like, is converted to a high-purity non-aqueous solution. A method of dissolving in a solvent, heating a non-aqueous solution obtained by dissolving a compound containing fluorine in a non-aqueous solvent under reduced pressure,
A method for evaporating and removing a trace amount of water and hydrogen fluoride contained therein, and a method for dissolving a compound containing fluorine in a non-aqueous solvent to obtain a non-aqueous solution by adsorption treatment with an adsorbent such as activated alumina to obtain hydrogen fluoride And the like.
Among them, the adsorption treatment is preferable because the operation is easy. The extent to which the content of hydrogen fluoride can be reduced by the adsorption treatment depends on the adsorbent used. For example, when activated alumina is washed with a dilute aqueous solution of nitric acid and then sufficiently washed with water and dried, the content of hydrogen fluoride can be easily reduced to several ppm. In the present invention, a compound containing fluorine is used as the electrolyte. Usually, a quaternary ammonium salt represented by the general formula (I) or quaternary ammonium salt
Grade phosphonium salts are used.

[0008]

[Formula 2] Q ⁺ X ^- ... (I)

Wherein Q ⁺ is a quaternary ammonium group or a quaternary phosphonium group, and X ⁻ is PF ₆ ⁻ , BF _{4
^{-, AsF 6 -, N (}} CF 3 SO 3) 2 -, C (CF 3
A counter ion selected from the group consisting of SO ₃ ) ₃ ⁻ , SbF ₆ ⁻ and RfSO ₃ ⁻ (Rf is a fluoroalkyl group having 1 to 8 carbon atoms). As the quaternary ammonium group represented by Q ⁺ , those obtained by quaternizing an arbitrary tertiary amine with an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, or the like are used. A hydroxyl group, an amino group, a nitro group, a cyano group, a carboxyl group, an ether group, an aldehyde group, and the like may be bonded to the hydrocarbon portion forming the quaternary ammonium group. The main quaternary ammonium groups are shown below.

Trialkylamine having a quaternized nitrogen; tetramethylammonium, ethyltrimethylammonium, diethyldimethylammonium, triethylmethylammonium, tetraethylammonium, trimethyl-n-propylammonium, trimethylisopropylammonium, ethyldimethyl-n -Propylammonium, ethyldimethylisopropylammonium, diethylmethyl-n-propylammonium, diethylmethylisopropylammonium, dimethyldi-n
-Propyl ammonium, dimethyl-n-propyl isopropyl ammonium, dimethyl diisopropyl ammonium, triethyl-n-propyl ammonium, n-
Butyltrimethylammonium, isobutyltrimethylammonium, t-butyltrimethylammonium, triethylisopropylammonium, ethylmethyldi-
n-propylammonium, ethylmethyl-n-propylisopropylammonium, ethylmethyldiisopropylammonium, n-butylethyldimethylammonium, isobutylethyldimethylammonium, t-butylethyldimethylammonium, diethyldi-n-propylammonium, diethyl-n-propyl Isopropyl ammonium, diethyl diisopropyl ammonium, methyl tri-n-propyl ammonium, methyl di-n-propyl isopropyl ammonium, methyl-n
-Propyldiisopropylammonium, n-butyltriethylammonium, isobutyltriethylammonium, t-butyltriethylammonium, di-n-butyldimethylammonium, diisobutyldimethylammonium, di-t-butyldimethylammonium, n-
Butyl isobutyl dimethyl ammonium, n-butyl-
t-butyldimethylammonium, isobutyl-t-butyldimethylammonium and the like.

A nitrogen atom of a pyrrolidine ring quaternized;
N, N-dimethylpyrrolidinium, N-ethyl-N-methylpyrrolidinium, N, N-diethylpyrrolidinium, 1,1,2-trimethylpyrrolidinium, 1,1,
3-trimethylpyrrolidinium, 1-ethyl-1,2-
Dimethylpyrrolidinium, 1-ethyl-1,3-dimethylpyrrolidinium, 2-ethyl-1,1-dimethylpyrrolidinium, 3-ethyl-1,1-dimethylpyrrolidinium, 1,1-diethyl- 2-methylpyrrolidinium,
1,1-diethyl-3-methylpyrrolidinium, 1,2
-Diethyl-1-methylpyrrolidinium, 1,3-diethyl-1-methylpyrrolidinium, 1,1,2-triethylpyrrolidinium, 1,1,3-triethylpyrrolidinium, 1,1,2 , 2-tetramethylpyrrolidinium, 1,1,2,3-tetramethylpyrrolidinium,
1,1,2,4-tetramethylpyrrolidinium, 1,
1,2,5-tetramethylpyrrolidinium, 1,1,
3,4-tetramethylpyrrolidinium, 1,1,3,3
-Tetramethylpyrrolidinium, 2-ethyl-1,1,1
2-trimethylpyrrolidinium, 2-ethyl-1,1,1,
3-trimethylpyrrolidinium, 3-ethyl-1,1,
2-trimethylpyrrolidinium, 3-ethyl-1,1,
3-trimethylpyrrolidinium, 2-ethyl-1,1,1,
4-trimethylpyrrolidinium, 4-ethyl-1,1,
2-trimethylpyrrolidinium, 2-ethyl-1,1,1,
5-trimethylpyrrolidinium, 3-ethyl-1,1,1
4-trimethylpyrrolidinium, 1-ethyl-1,2,2
2-trimethylpyrrolidinium, 1-ethyl-1,2,2
3-trimethylpyrrolidinium, 1-ethyl-1,3,
3-trimethylpyrrolidinium, 1-ethyl-1,2,2
4-trimethylpyrrolidinium, 1-ethyl-1,2,2
5-trimethylpyrrolidinium, 1-ethyl-1,3,
4-trimethylpyrrolidinium, 2,2-diethyl-
1,1-dimethylpyrrolidinium, 2,3-diethyl-
1,1-dimethylpyrrolidinium, 3,3-diethyl-
1,1-dimethylpyrrolidinium, 2,4-diethyl-
1,1-dimethylpyrrolidinium, 2,5-diethyl-
1,1-dimethylpyrrolidinium, 3,4-diethyl-
1,1-dimethylpyrrolidinium, 1,2-diethyl-
1,2-dimethylpyrrolidinium, 1,2-diethyl-
1,3-dimethylpyrrolidinium, 1,3-diethyl-
1,2-dimethylpyrrolidinium, 1,3-diethyl-
1,3-dimethylpyrrolidinium, 1,2-diethyl-
1,4-dimethylpyrrolidinium, 1,4-diethyl-
1,2-dimethylpyrrolidinium, 1,2-diethyl-
1,5-dimethylpyrrolidinium, 1,3-diethyl-
1,4-dimethylpyrrolidinium, 1,1,2,2,3
-Pentamethylpyrrolidinium, 1,1,2,2,4-
Pentamethylpyrrolidinium, 1,1,2,2,5-pentamethylpyrrolidinium, 1,1,2,3,4-pentamethylpyrrolidinium, 1,1,2,3,5-pentamethyl Pyrrolidinium, 1,1,3,3,4-pentamethylpyrrolidinium, 1,1,3,3,5-pentamethylpyrrolidinium, 1-ethyl-1,2,2,3-tetramethyl Pyrrolidinium, 1-ethyl-1,2,2,4
-Tetramethylpyrrolidinium, 1-ethyl-1,2,2
2,5-tetramethylpyrrolidinium, 1-ethyl-
1,2,3,4-tetramethylpyrrolidinium, 1-ethyl-1,2,3,5-tetramethylpyrrolidinium,
1-ethyl-1,2,4,5-tetramethylpyrrolidinium, 1-ethyl-1,3,3,4-tetramethylpyrrolidinium, 1-ethyl-1,3,3,5-tetramethyl Pyrrolidinium, 2-ethyl-1,1,2,3-tetramethylpyrrolidinium, 2-ethyl-1,1,2,4
-Tetramethylpyrrolidinium, 2-ethyl-1,1,1
2,5-tetramethylpyrrolidinium, 2-ethyl-
1,1,3,3-tetramethylpyrrolidinium, 2-ethyl-1,1,3,4-tetramethylpyrrolidinium,
2-ethyl-1,1,3,5-tetramethylpyrrolidinium, 2-ethyl-1,1,4,4-tetramethylpyrrolidinium, 2-ethyl-1,1,4,5-tetramethyl Pyrrolidinium, 2-ethyl-1,1,5,5-tetramethylpyrrolidinium, 3-ethyl-1,1,2,2
-Tetramethylpyrrolidinium, 3-ethyl-1,1,
2,3-tetramethylpyrrolidinium, 3-ethyl-
1,1,2,4-tetramethylpyrrolidinium, 3-ethyl-1,1,2,5-tetramethylpyrrolidinium,
3-ethyl-1,1,3,4-tetramethylpyrrolidinium, 3-ethyl-1,1,4,4-tetramethylpyrrolidinium, 3-ethyl-1,1,4,5-tetramethyl Pyrrolidinium, 1,1,2,2,3,3-hexamethylpyrrolidinium, 1,1,2,2,3,4-hexamethylpyrrolidinium, 1,1,2,2,3, 5-hexamethylpyrrolidinium, 1,1,2,2,4,4-hexamethylpyrrolidinium, 1,1,2,2,4,5-
Hexamethylpyrrolidinium, 1,1,2,2,5,5
Hexamethylpyrrolidinium, 1,1,2,3,3
4-hexamethylpyrrolidinium, 1,1,2,3
3,5-hexamethylpyrrolidinium, 1,1,2,2
3,4,4-hexamethylpyrrolidinium, 1,1,
2,3,5,5-hexamethylpyrrolidinium, 1,
1,2,3,4,5-hexamethylpyrrolidinium and the like.

Morpholine ring in which nitrogen in the quaternary is quaternized N, N-dimethylmorpholinium, N-ethyl-N-methylmorpholinium, N, N-diethylmorpholinium, 3,4,4-trimethyl Morpholinium, 2,4
4-trimethylmorpholinium, 3-ethyl-4,4-
Dimethylmorpholinium, 2-ethyl-4,4-dimethylmorpholinium, 3,4-dimethyl-4-ethylmorpholinium, 2,4-dimethyl-4-ethylmorpholinium, 3-methyl-4, 4-diethylmorpholinium,
2-methyl-4,4-diethylmorpholinium, 3,4
-Diethyl-4-methylmorpholinium, 2,4-diethyl-4-methylmorpholinium, 3,4,4-triethylmorpholinium, 2,4,4-triethylmorpholinium, 3,3,4 2,4-tetramethylmorpholinium, 2,3,4,4-tetramethylmorpholinium,
2,4,4,5-tetramethylmorpholinium, 3,
4,4,5-tetramethylmorpholinium, 2,2
4,4-tetramethylmorpholinium, 2,4,4,6
-Tetramethylmorpholinium, 2,4,4-trimethyl-3-ethylmorpholinium, 2-ethyl-3,4
4-trimethylmorpholinium, 2,4,4-trimethyl-5-ethylmorpholinium, 2-ethyl-4,4
5-trimethylmorpholinium, 3-ethyl-4,4,
5-trimethylmorpholinium, 2-ethyl-4,4,
6-trimethylmorpholinium, 2,3-dimethyl-
4,4-diethylmorpholinium, 25-dimethyl-
4,4-diethylmorpholinium, 3,5-dimethyl-
4,4-diethylmorpholinium, 2,6-dimethyl-
4,4-diethylmorpholinium, 2,4-dimethyl-
3,4-diethylmorpholinium, 2,4-diethyl-
3,4-dimethylmorpholinium, 2,4-dimethyl-
4,5-diethylmorpholinium, 2,4-diethyl-
4,5-dimethylmorpholinium, 3,4-diethyl-
4,5-dimethylmorpholinium, 2,4-diethyl-
4,6-dimethylmorpholinium, 2,3-diethyl-
4,4-dimethylmorpholinium, 2,5-diethyl-
4,4-dimethylmorpholinium, 3,5-diethyl-
4,4-dimethylmorpholinium, 2,6-diethyl-
4,4-dimethylmorpholinium, 2,3,4,4,6
-Pentamethylmorpholinium, 2,3,4,4,5-
Pentamethylmorpholinium, 2,4,4,6-tetramethyl-3-ethylmorpholinium, 2,4,4,5-
Tetramethyl-3-ethylmorpholinium, 2-ethyl-3,4,4,6-tetramethylmorpholinium, 2-
Ethyl-3,4,4,5-tetramethylmorpholinium, 2,3,4,4,5,6-hexamethylmorpholinium and the like.

[0013] The nitrogen of the imidazoline ring is quaternized; N, N'-dimethylimidazolinium, N-ethyl-N'-methylimidazolinium, N, N'-diethylimidazolinium, 1,2 1,3-trimethylimidazolinium, 1,3,4-trimethylimidazolinium, 1
-Ethyl-2,3-dimethylimidazolinium, 1-ethyl-3,4-dimethylimidazolinium, 1-ethyl-3,5-dimethylimidazolinium, 2-ethyl-
1,3-dimethylimidazolinium, 4-ethyl-1,
3-dimethylimidazolinium, 1,2-diethyl-3
-Methylimidazolinium, 1,4-diethyl-3-methylimidazolinium, 1,5-diethyl-3-methylimidazolinium, 1,3-diethyl-2-methylimidazolinium, 1,3-diethyl -4-methylimidazolinium, 1,2,3-triethylimidazolinium,
1,3,4-triethylimidazolinium, 1,2,2
3,4-tetramethylimidazolinium, 1-ethyl-
2,3,4-trimethylimidazolinium, 1-ethyl-2,3,5-trimethylimidazolinium, 1-ethyl-3,4,5-trimethylimidazolinium, 2-ethyl-1,3,4 -Trimethylimidazolinium, 4-
Ethyl-1,2,3-trimethylimidazolinium,
1,2-diethyl-3,4-dimethylimidazolinium, 1,3-diethyl-2,4-dimethylimidazolinium, 1,4-diethyl-2,3-dimethylimidazolinium, 2,4-diethyl -1,3-dimethylimidazolinium, 4,5-diethyl-1,3-dimethylimidazolinium, 1,2,3-triethyl-4-methylimidazolinium, 1,2,4-triethyl-3- Methyl imidazolinium, 1,2,5-triethyl-3-methyl imidazolinium, 1,3,4-triethyl-2-methyl imidazolinium, 1,3,4-triethyl-5-methyl imidazolinium, 1,4,5-triethyl-3-
Methyl imidazolinium, 1,2,3,4,5-pentamethyl imidazolinium and the like.

[0014] N, N'-dimethyltetrahydropyrimidinium, N-
Ethyl-N'-methyltetrahydropyrimidinium,
N, N'-diethyltetrahydropyrimidinium, 1,
2,3-trimethyltetrahydropyrimidinium, 1,
3,4-trimethyltetrahydropyrimidinium, 1,
3,5-trimethyltetrahydropyrimidinium, 1-
Ethyl-2,3-dimethyltetrahydropyrimidinium, 1-ethyl-3,4-dimethyltetrahydropyrimidinium, 1-ethyl-3,5-dimethyltetrahydropyrimidinium, 1-ethyl-3,6-dimethyltetrahydro Pyrimidinium, 2-ethyl-1,3-dimethyltetrahydropyrimidinium, 4-ethyl-1,3-dimethyltetrahydropyrimidinium, 5-ethyl-1,
3-dimethyltetrahydropyrimidinium, 1,2,
3,4-tetramethyltetrahydropyrimidinium,
1,2,3,5-tetramethyltetrahydropyrimidinium, 1-ethyl-2,3,4-trimethyltetrahydropyrimidinium, 1-ethyl-2,3,5-trimethyltetrahydropyrimidinium, 1-ethyl −2,3
6-trimethyltetrahydropyrimidinium, 2-ethyl-1,3,4-trimethyltetrahydropyrimidinium, 2-ethyl-1,3,5-trimethyltetrahydropyrimidinium, 4-ethyl-1,2,3- Trimethyltetrahydropyrimidinium, 4-ethyl-1,3,5
-Trimethyltetrahydropyrimidinium, 4-ethyl-1,3,6-trimethyltetrahydropyrimidinium, 5-ethyl-1,2,3-trimethyltetrahydropyrimidinium, 5-ethyl-1,3,4-trimethyl Tetrahydropyrimidinium, 1,2-diethyl-3,
4-dimethyltetrahydropyrimidinium, 1,2-diethyl-3,5-dimethyltetrahydropyrimidinium, 1,2-diethyl-3,6-dimethyltetrahydropyrimidinium, 1,3-diethyl-2,4- Dimethyltetrahydropyrimidinium, 1,3-diethyl-2,
5-dimethyltetrahydropyrimidinium, 1,4-diethyl-2,3-dimethyltetrahydropyrimidinium, 1,4-diethyl-3,5-dimethyltetrahydropyrimidinium, 1,4-diethyl-3,6- Dimethyltetrahydropyrimidinium, 1,5-diethyl-2,
3-dimethyltetrahydropyrimidinium, 1,5-diethyl-3,4-dimethyltetrahydropyrimidinium, 1,5-diethyl-3,6-dimethyltetrahydropyrimidinium, 2,4-diethyl-1,3- Dimethyltetrahydropyrimidinium, 2,5-diethyl-1,1,
3-dimethyltetrahydropyrimidinium, 4,5-diethyl-1,3-dimethyltetrahydropyrimidinium, 4,6-diethyl-1,3-dimethyltetrahydropyrimidinium, 1,2,3,4,5- Pentamethyltetrahydropyrimidinium, 1,2,3,4,6-pentamethyltetrahydropyrimidinium, 1,2,3
4,5,6-Hexamethyltetrahydropyrimidinium, 5-methyl-1,5-diazabicyclo [4.3.
0] -5-nonenium, 5-ethyl-1,5-diazabicyclo [4.3.0] -5-nonenium, 5-methyl-
1,5-diazabicyclo [5.4.0] -5-undecenium, 5-ethyl-1,5-diazabicyclo [5.
4.0] -5-undecenium and the like.

A nitrogen atom on the piperazine ring quaternized;
N, N, N ', N'-tetramethylpiperazinium, N
-Ethyl-N, N ', N'-trimethylpiperazinium, N, N-diethyl-N', N'-dimethylpiperazinium, N, N, N'-triethyl-N'-methylpiperazinium, N, N, N ', N'-tetraethylpiperazinium, 1,1,2,4,4-pentamethylpiperazinium, 1,1,3,4,4-pentamethylpiperazinium, 1,1 , 2,3,4,4-hexamethylpiperazinium, 1,1,2,4,4,5-hexamethylpiperazinium, 1,1,2,4,4,6-hexamethylpiperazinium 1,1,3,4,4,5-hexamethylpiperazinium, 1-ethyl-1,2,4,4-tetramethylpiperazinium, 1-ethyl-1,3,4,4-tetra Methylpiperazinium, 2-ethyl-1,1,4,
4-tetramethylpiperazinium, 1-ethyl-1,
2,4,4-tetramethylpiperazinium, 1-ethyl-1,3,4,4-tetramethylpiperazinium, 1,
1-diethyl-2,4,4-trimethylpiperazinium, 1,4-diethyl-1,2,4-trimethylpiperazinium, 1,2-diethyl-1,4,4-trimethylpiperazinium, 1 , 3-diethyl-1,4,4-trimethylpiperazinium and the like.

A quaternized nitrogen of the piperidine ring;
N, N-dimethylpiperidinium, N-ethyl-N-methylpiperidinium, N, N-diethylpiperidinium, 1,1,2-trimethylpiperidinium, 1,1,
3-trimethylpiperidinium, 1,1,4-trimethylpiperidinium, 1,2,2-tetramethylpiperidinium, 1,1,2,3-tetramethylpiperidinium, 1,1,2,2 4-tetramethylpiperidinium,
1,1,2,5-tetramethylpiperidinium, 1,
1,2,6-tetramethylpiperidinium, 1,1,
3,3-tetramethylpiperidinium, 1,1,3,4
-Tetramethylpiperidinium, 1,1,3,5-tetramethylpiperidinium, 1-ethyl-1,2-dimethylpiperidinium, 1-ethyl-1,3-dimethylpiperidinium, 1-ethyl -1,4-dimethylpiperidinium, 1-ethyl-1,2,3-trimethylpiperidinium, 1-ethyl-1,2,4-trimethylpiperidinium, 1-ethyl-1,2,5- Trimethylpiperidinium, 1-ethyl-1,2,6-trimethylpiperidinium, 1-ethyl-1,3,4-trimethylpiperidinium, 1-ethyl-1,3,5-trimethylpiperidinium, 1,1-diethyl-2-methylpiperidinium,
1,1-diethyl-3-methylpiperidinium, 1,1
-Diethyl-4-methylpiperidinium, 1,1-diethyl-2,3-dimethylpiperidinium, 1,1-diethyl-2,4-dimethylpiperidinium, 1,1-diethyl-2,5- Dimethylpiperidinium, 1,1-diethyl-2,6-dimethylpiperidinium, 1,1-diethyl-3,4-dimethylpiperidinium, 1,1-diethyl-3,5-dimethylpiperidinium, 2-ethyl-
1,1,3-trimethylpiperidinium, 2-ethyl-
1,1,4-trimethylpiperidinium, 2-ethyl-
1,1,5-trimethylpiperidinium, 2-ethyl-
1,1,6-trimethylpiperidinium, 3-ethyl-
1,1,2-trimethylpiperidinium, 3-ethyl-
1,1,4-trimethylpiperidinium, 3-ethyl-
1,1,5-trimethylpiperidinium, 3-ethyl-
1,1,6-trimethylpiperidinium, 4-ethyl-
1,1,2-trimethylpiperidinium, 4-ethyl-
1,1,3-trimethylpiperidinium, 1,2-diethyl-1,3-dimethylpiperidinium, 1-ethyl-
1,2,4-trimethylpiperidinium, 1,2-diethyl-1,5-dimethylpiperidinium, 1,2-diethyl-1,6-dimethylpiperidinium, 1,3-diethyl-1,5 -Dimethylpiperidinium, 1,3-diethyl-1,4-dimethylpiperidinium, 1,3-diethyl-1,6-dimethylpiperidinium, 1,4-diethyl-1,2-dimethylpiperidinium , 1,4-diethyl-1,3-dimethylpiperidinium, 1,1,2-
Triethyl-3-methylpiperidinium, 1,1,2-
Triethyl-4-methylpiperidinium, 1,1,2-
Triethyl-5-methylpiperidinium, 1,1,2-
Triethyl-6-methylpiperidinium, 1,1,3-
Triethyl-2-methylpiperidinium, 1,1,3-
Triethyl-4-methylpiperidinium, 1,1,3-
Triethyl-5-methylpiperidinium, 1,1,3-
Triethyl-6-methylpiperidinium, 1,1,4-
Triethyl-2-methylpiperidinium, 1,1,4-
Triethyl-3-methylpiperidinium, 2-ethyl-
1,1-dimethylpiperidinium, 3-ethyl-1,1
-Dimethylpiperidinium, 4-ethyl-1,1-dimethylpiperidinium, 2,3-diethyl-1,1-dimethylpiperidinium, 2,4-diethyl-1,1-dimethylpiperidinium, 2 , 5-Diethyl-1,1-dimethylpiperidinium, 2,6-diethyl-1,1-dimethylpiperidinium, 3,4-diethyl-1,1-dimethylpiperidinium, 3,5-diethyl- 1,1-dimethylpiperidinium, 1,2-diethyl-1-methylpiperidinium, 1,3-diethyl-1-methylpiperidinium, 1,4-diethyl-1-methylpiperidinium, 2,3-triethyl-1-methylpiperidinium, 1,2,4-triethyl-1-methylpiperidinium, 1,2,5-triethyl-1-methylpiperidinium, 1,2,6-to Ethyl-1-methylpiperidinium, 1,3,4-triethyl-1-methylpiperidinium, 1,3,5-triethyl-1-methylpiperidinium, 1,1,2-triethylpiperidinium, 1,1,
4-triethylpiperidinium, 1,1,2,3-tetraethylpiperidinium, 1,1,2,4-tetraethylpiperidinium, 1,1,2,5-tetraethylpiperidinium, 1,1, 2,6-tetraethylpiperidinium, 1,1,3,4-tetramethylpiperidinium,
1,1,3,5-tetraethylpiperidinium and the like.

Pyridine ring having quaternized nitrogen; N
-Methylpyridinium, N-ethylpyridinium, 1,
2-dimethylpyridinium, 1,3-dimethylpyridinium, 1,4-dimethylpyridinium, 1-ethyl-2
-Methylpyridinium, 2-ethyl-1-methylpyridinium, 1-ethyl-3-methylpyridinium, 3-ethyl-1-methylpyridinium, 1-ethyl-4-methylpyridinium, 4-ethyl-1-methylpyridinium, 1,2-diethylpyridinium, 1,3-diethylpyridinium, 1,4-diethylpyridinium, 1,
2,3-trimethylpyridinium, 1,2,4-trimethylpyridinium, 1,3,4-trimethylpyridinium, 1,3,5-trimethylpyridinium, 1,2,5
-Trimethylpyridinium, 1,2,6-trimethylpyridinium, 1-ethyl-2,3-dimethylpyridinium, 1-ethyl-2,4-dimethylpyridinium, 1-
Ethyl-2,5-dimethylpyridinium, 1-ethyl-
2,6-dimethylpyridinium, 1-ethyl-3,4-
Dimethylpyridinium, 1-ethyl-3,5-dimethylpyridinium, 2-ethyl-1,3-dimethylpyridinium, 2-ethyl-1,4-dimethylpyridinium, 2
-Ethyl-1,5-dimethylpyridinium, 2-ethyl-1,6-dimethylpyridinium, 3-ethyl-1,2
-Dimethylpyridinium, 3-ethyl-1,4-dimethylpyridinium, 3-ethyl-1,5-dimethylpyridinium, 3-ethyl-1,6-dimethylpyridinium,
4-ethyl-1,2-dimethylpyridinium, 4-ethyl-1,3-dimethylpyridinium, 1,2-diethyl-3-methylpyridinium, 1,2-diethyl-4-methylpyridinium, 1,2-diethyl- 5-methylpyridinium, 1,2-diethyl-6-methylpyridinium, 1,3-diethyl-2-methylpyridinium, 1,
3-diethyl-4-methylpyridinium, 1,3-diethyl-5-methylpyridinium, 1,3-diethyl-6
-Methylpyridinium, 1,4-diethyl-2-methylpyridinium, 1,4-diethyl-3-methylpyridinium, 2,3-diethyl-1-methylpyridinium,
2,4-diethyl-1-methylpyridinium, 2,5-
Diethyl-1-methylpyridinium, 2,6-diethyl-1-methylpyridinium, 3,4-diethyl-1-methylpyridinium, 3,5-diethyl-1-methylpyridinium, 1,2,3,4,5- Pentamethylpyridinium, 1,2,3,4,6-pentamethylpyridinium, 1,2,3,5,6-pentamethylpyridinium,
1,2,3,4,5,6-hexamethylpyridinium and the like.

N, N'-dimethylimidazolium, N-ethyl-, wherein the nitrogen of the imidazole ring is quaternized
N'-methylimidazolium, N, N'-diethylimidazolium, 1,2,3-trimethylimidazolium,
1,3,4-trimethylimidazolium, 1-ethyl-
2,3-dimethylimidazolium, 1-ethyl-3,4
-Dimethylimidazolium, 1-ethyl-3,5-dimethylimidazolium, 2-ethyl-1,3-dimethylimidazolium, 4-ethyl-1,3-dimethylimidazolium, 1,2-diethyl-3-methyl Imidazolium, 1,4-diethyl-3-methylimidazolium,
1,5-diethyl-3-methylimidazolium, 1,3
-Diethyl-2-methylimidazolium, 1,3-diethyl-4-methylimidazolium, 1,2,3-triethylimidazolium, 1,3,4-triethylimidazolium, 1,2,3,4-tetra Methylimidazolium, 1-ethyl-2,3,4-trimethylimidazolium, 1-ethyl-2,3,5-trimethylimidazolium, 1-ethyl-3,4,5-trimethylimidazolium, 2-ethyl- 1,3,4-trimethylimidazolium, 4-ethyl-1,2,3-trimethylimidazolium, 1,2-diethyl-3,4-dimethylimidazolium, 1,3-diethyl-2,4-dimethylimidazo Lium, 1,4-diethyl-2,3-dimethylimidazolium, 1,4-diethyl-2,5-dimethylimidazolium, 2,4-diethyl -1,3-dimethylimidazolium, 4,5-diethyl-1,3-dimethylimidazolium, 1,2,3-triethyl-4-methylimidazolium, 1,2,4-triethyl-3-methylimidazolium , 1,2,5-triethyl-3-methylimidazolium, 1,3,4-triethyl-2-methylimidazolium, 1,3,4-triethyl-5-methylimidazolium, 1,4,5-triethyl -3-methylimidazolium, 1,2,3,4,5-pentamethylimidazolium and the like.

The quaternary phosphonium group represented by Q ⁺ usually has a central carbon atom such as an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group or the like having 1 carbon atom.
Those having -20, preferably 1-5 hydrocarbon groups bonded thereto are used. Two or three of these hydrocarbon groups may be mutually bonded to form a ring. Further, a substituent such as a hydroxyl group, an amino group, a nitro group, a cyano group, a carboxyl group, an ether group, or an aldehyde group may be bonded to these hydrocarbon groups. As the quaternary phosphonium group, for example, the following are used.

Tetramethylphosphonium, ethyltrimethylphosphonium, diethyldimethylphosphonium, triethylmethylphosphonium, tetraethylphosphonium, trimethyl-n-propylphosphonium, trimethylisopropylphosphonium, ethyldimethyl-n-propylphosphonium, ethyldimethylisopropylphosphonium, diethylmethyl-n -Propylphosphonium, diethylmethylisopropylphosphonium, dimethyldi-n-propylphosphonium, dimethyl-n-propylisopropylphosphonium, dimethyldiisopropylphosphonium, triethyl-n-propylphosphonium, n-butyltrimethylphosphonium, isobutyltrimethylphosphonium, t-butyltrimethylphosphonium , Triethyloy Propyl phosphonium, Echirumechiruji -n- propyl phosphonium, ethyl methyl -n
-Propylisopropylphosphonium, ethylmethyldiisopropylphosphonium, n-butylethyldimethylphosphonium, isobutylethyldimethylphosphonium, t-butylethyldimethylphosphonium, diethyldi-n-propylphosphonium, diethyl-n-propylisopropylphosphonium, diethyldiisopropylphosphonium, methyltri- n-propylphosphonium, methyldi-n-propylisopropylphosphonium, methyl-n-propyldiisopropylphosphonium, n-butyltriethylphosphonium, isobutyltriethylphosphonium, t-butyltriethylphosphonium, di-n-butyldimethylphosphonium, diisobutyldimethylphosphonium, -T-butyldimethylphosphonium, n-butylyl Butyldimethyl phosphonium, n- butyl -t- butyl dimethyl phosphonium, such as isobutyl -t- butyl dimethyl phosphonium.

The concentration of the electrolyte comprising the fluorine-containing compound in the non-aqueous electrolyte is suitably from 0.1 to 3.0 M / l, particularly preferably from 0.5 to 1.5 M / l. If the concentration is too low, the internal resistance increases due to the low conductivity of the electrolytic solution. On the other hand, if the temperature is too high, salts may be precipitated at a low temperature to cause a problem. The non-aqueous solvent for the electrolytic solution is not particularly limited, and ethylene carbonate, propylene carbonate, butylene carbonate, gamma-butyrolactone, acetonitrile, dimethylformamide, sulfolane, and the like may be used alone or in a mixture of some. I just need. In addition, dimethyl carbonate, ethyl methyl carbonate, chain carbonates such as diethyl carbonate, methyl acetate,
An aliphatic monocarboxylic acid ester such as methyl propylene acid may be appropriately mixed and used.

[0022]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. The content of hydrogen fluoride in the electrolyte and the characteristics of the electric double layer capacitor manufactured using the electrolyte were measured as follows.

Hydrogen fluoride content: 10 g of the electrolytic solution was precisely weighed into a stoppered flask using an analytical balance. 0 ℃
Was added to make a total of 100 ml, and then titrated with a 1/10 normal aqueous sodium hydroxide solution using bromthymol blue as an indicator. The point at which the solution changed from orange to blue-violet and lasted for 5 seconds was the end point of the titration. The content of hydrogen fluoride is calculated by the following equation. C = (0.002 × A × F / S) × 10 ⁶ where C: content of hydrogen fluoride (ppm) A: amount of sodium hydroxide aqueous solution required for titration (ml) F: sodium hydroxide aqueous solution Factor S: Weight of electrolyte (g)

Characteristics of electric double-layer capacitor: 1 part by weight of polytetrafluoroethylene was added to 10 parts by weight of activated carbon powder (specific surface area: 2000 m ² / g), water was further added and wet-kneaded, and then a sheet having a thickness of 0.7 mm was obtained. Molded. This sheet was punched into a disk having a diameter of 15 mm and heated to evaporate water to produce a polarizable electrode. This polarizable electrode 2
The sheets were opposed to each other via a separator made of a nonwoven fabric made of polypropylene and placed in a container made of a stainless steel can and a lid. After pouring the electrolytic solution into the polarizable electrode and the separator to sufficiently impregnate the electrolytic solution, the ends of the can and the lid are caulked and closed via a polypropylene packing, and have a diameter of 20 mm and a thickness of 2 mm. A 2.0 mm electric double layer capacitor was manufactured.

With respect to this electric double layer capacitor,
The initial capacity and internal resistance when a voltage of 8 V was applied were measured. Further, the capacity after storing at 70 ° C. for 1000 hours while applying a voltage of 2.8 V was measured, and the capacity deterioration rate from the initial capacity was calculated. The internal resistance is 1k frequency.
It measured by the alternating current two-terminal method in Hz. Example 1 and Comparative Example 1

High-purity propylene carbonate is added to triethylmethylammonium tetrafluoroborate (Et ₃ MeN
⁺ .BF ₄ ⁻ ) was dissolved at 1 mol / l to prepare an electrolytic solution. After adding 1 part by weight of high-purity propylene carbonate to 10 parts by weight of this electrolytic solution, the mixture was heated to a kettle temperature of 120 ° C. under reduced pressure of 5 mmHg to distill out 1 part by weight of propylene carbonate, and the electrolytic solution was recovered. Table 1 shows the hydrogen fluoride content of these electrolytes and the characteristics of electric double-layer capacitors manufactured using them.

Example 2 and Comparative Example 2 In a dry nitrogen atmosphere at room temperature and a dew point of -60 ° C., tetraethylammonium tetrafluoroborate (Et ₄ N ⁺ .BF ₄ ⁻ ) was added to 1 mol / l of high-purity propylene carbonate. Was dissolved to prepare an electrolytic solution. Activated alumina (AC-11, specific surface area 140 m ² / g, average particle size 80 to 100 μm, product of SMIAL PRODUCTS CO., LTD.) Was washed with 100% by weight of this electrolytic solution with 1% diluted nitric acid, and then thoroughly washed with water. After drying at 550 ° C. for 4 hours, 1 part by weight was added, and the mixture was stirred for 30 minutes and then filtered to collect an electrolyte. Table 1 shows the hydrogen fluoride content of these electrolytes and the characteristics of electric double-layer capacitors manufactured using them.

Comparative Example 3 Tetraethylphosphonium tetrafluoroborate (Et ₄ P ⁺ .BF ₄ ⁻ ) was dissolved in high-purity propylene carbonate in a dry nitrogen atmosphere at a dew point of −60 ° C. at room temperature to a concentration of 1 mol / l. Thus, an electrolytic solution was prepared. Table 1 shows the content of hydrogen fluoride in this electrolytic solution and the characteristics of electric double layer capacitors manufactured using the same.

Example 3 The same tetraethylphosphonium tetrafluoroborate (40 g) as used in Comparative Example 2 was added to methanol (100 g), dissolved by heating at 64 ° C., and filtered while hot. The filtrate was gradually cooled to 5 ° C., and the precipitated crystals were collected by filtration, washed with methanol at 5 ° C., and dried under reduced pressure. An electrolytic solution was prepared in exactly the same manner as in Comparative Example 3, except that tetraethylphosphonium tetrafluoroborate purified by this recrystallization was used. Table 1 shows the content of hydrogen fluoride in the electrolytic solution and the characteristics of electric double layer capacitors manufactured using the same.

[0030]

[Table 1]

Claims (3)

[Claims] 1. A non-aqueous electrolytic solution in which a compound containing fluorine is dissolved as an electrolyte in a non-aqueous solvent, wherein the non-aqueous electrolytic solution for an electric double layer capacitor has a hydrogen fluoride content of 30 ppm or less. liquid. 2. The non-aqueous electrolyte according to claim 1, wherein the fluorine-containing compound is a quaternary ammonium salt or a quaternary phosphonium salt represented by the general formula (I). ## STR1 ## ^{Q + X - ... (I)} ( wherein, Q ⁺ represents a quaternary ammonium group or quaternary phosphonium group, X ^- is _{^{PF 6 -, BF 4 -,}} AsF 6
_{^{-, N (CF 3 SO 3}} ) 2 -, C (CF 3 S
Represents a counter ion selected from the group consisting of O ₃ ) ₃ ⁻ , SbF ₆ ⁻ and RfSO ₃ ⁻ (Rf is a fluoroalkyl group having 1 to 8 carbon atoms). ) 3. The non-aqueous solvent is propylene carbonate,
The non-aqueous water according to claim 1, wherein at least a component selected from the group consisting of ethylene carbonate, butylene carbonate, sulfolane, methylsulfolane, dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate is used as a main component. Electrolyte.