JPH11340101A - Electrolytic solution for electric double layer capacitor and electric double layer capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise the withstand voltage of an electrolyte for electric double layer capacitor by using the derivative of γ-butyrolactone containing one or more ethyl groups which are electron donating substituent groups introduced to its α,β-, or γ-position as the solvent of the electrolyte. SOLUTION: An electrolyte for driving electric double layer capacitor is composed of an organic solvent-based electrolyte prepared by dissolving an electrolytic salt in an organic solvent and contains γ-butyrolactone containing one or more ethyl, groups introduced to its α-,β-, or γ-position as the organic solvent. An electric double layer capacitor uses the electrolyte. When this electrolyte is used, the electron density of carbon becomes higher in the 'COOH' part of the electrolyte and hydrolytic reactions are suppressed, resulting in a higher oxidative destruction potential. When one or more ethyl groups are contained, however, the effect of the electrolyte does not change even when the other substituent group is a methyl group or butyl group. It is also possible to mix sulfolane, etc., in the derivative of γ-butyrolactone used as the solvent of the electrolyte.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic solvent-based electrolytic solution used for driving an electric double layer capacitor and an electric double layer capacitor using the same.

[0002]

2. Description of the Related Art There are two types of conventional electrolytes for electric double layer capacitors: aqueous electrolytes and organic solvent electrolytes.
In general, an organic solvent-based electrolyte has a wider potential window and is often used.

The organic solvent-based electrolyte uses γ-butyrolactone, propylene carbonate, ethylene carbonate, N, N-dimethylformamide or the like as a main solvent, and an organic acid salt such as tetraethylammonium tetrafluoroborate as a supporting electrolyte. , Or those containing an inorganic acid salt are often used. In particular, when γ-butyrolactone is used as the main solvent, the potential window is larger than that of other carbonate solvents, and the temperature characteristics are good.

[0004]

However, in an electrolytic solution using γ-butyrolactone as a main solvent,
Not only is there a trace amount of water, but also the -COO- moiety of the lactone ring shown in Chemical Formula 1 undergoes hydrolysis, and this has the problem that the oxidation potential of the electrolytic solution is significantly reduced [M. Ue, K. Ida, S. Mori, JE
electrochem. Soc., 141, 2989 (1
994)].

[0005]

Embedded image

An object of the present invention is to solve the above problems and to provide an electrolytic solution for an electric double layer capacitor having a high withstand voltage and an electric double layer capacitor having a large capacity using the same.

[0007]

Means for Solving the Problems The inventors of the present invention have made intensive efforts to develop an electrolytic solution having a higher withstand voltage, and as a result, the α-, β-, or γ-position which has not been used as an electrolyte solvent has been developed. By using a derivative of γ-butyrolactone in which one or more ethyl groups that are electron donating substituents are introduced, the electron density of carbon in the —COO— portion increases, and the hydrolysis reaction can be suppressed, It has been found that the oxidative decomposition potential can be increased.

[0008] That is, the present invention is an organic solvent-based electrolyte solution in which an electrolyte salt is dissolved in an organic solvent, the electrolyte solution for an electric double layer capacitor containing a derivative of γ-butyrolactone as the organic solvent.

Further, the present invention provides the above electrolyte solution for an electric double layer capacitor, wherein the γ-butyrolactone derivative has one or more ethyl groups at the α-position, β-position or γ-position carbon on the lactone ring. is there.

Further, the present invention is an electric double layer capacitor using the above-mentioned electrolytic solution.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to an organic solvent-based electrolytic solution in which an electrolyte salt is dissolved in an organic solvent.
Γ in which one or more ethyl groups are introduced at the position, β position, or γ position
-An electrolytic solution for driving an electric double layer capacitor containing butyrolactone and an electric double layer capacitor using the same.

According to the electrolytic solution for an electric double layer capacitor having the above structure, the electron density of carbon in the -COO- portion is increased, and the hydrolysis reaction is suppressed, so that the oxidative decomposition potential can be increased. However, as long as one or more ethyl groups are contained, even if the other substituent is a methyl group or a butyl group, the effect is not changed.

As a solvent of the organic solvent-based electrolyte of the present invention, it is possible to use a mixture of a derivative of γ-butyrolactone and another known solvent. However, in that case, it must be compatible with the γ-butyrolactone derivative of the present invention and must not inhibit the function as an electrolytic solution.
For example, propylene carbonate, ethylene carbonate, N, N-dimethylformamide, acetonitrile, sulfolane and the like can be mentioned. In the case of a mixed solvent,
The content of the derivative of γ-butyrolactone is 50 wt% or more and 100 wt% or more in order to sufficiently exert the effects of the present invention.
% Or less is desirable, but not particularly limited thereto.

The solute of the electrolytic solution of the present invention is not particularly limited, and those generally used as an electrolyte for an organic solvent-based electrolytic solution, for example, tetraethylammonium perchlorate, lithium perchlorate, Examples thereof include tetraethylammonium tetrafluoroborate, tetrabutylammonium tetrafluorophosphate, and tetraethylammonium hexafluorophosphate.

The solute concentration of the organic solvent-based electrolyte of the present invention is
Preferably it is 0.3 mol / l or more and 1.5 mol / l or less. When the solute concentration is too low, the function as an electrolyte becomes insufficient because the amount of ions for transferring charges is small. In addition, even if it is too high, the viscosity of the electrolyte solution becomes high, so that the conductivity is reduced, which causes an increase in internal resistance.

[0016]

The present invention will be specifically described below with reference to examples and comparative examples.

Example 1 An electrolytic solution of the present invention was prepared by dissolving tetraethylammonium tetrafluoroborate in α-ethyl-γ-butyrolactone at a concentration of 0.5 mol / l.

Using this electrolyte, a silver / silver chloride electrode as a reference electrode, a glassy carbon electrode as a counter electrode, and a glassy carbon electrode as a working electrode, in a glove box at 25 ° C. in a dry nitrogen atmosphere at 10 mV /
The potential was swept in sec to obtain a current-potential curve. From this current-potential curve, the oxidative decomposition potential and the reductive decomposition potential of the electrolytic solution were measured to determine a potential window.

(Example 2) An electrolytic solution was prepared in the same manner as in Example 1 except that β-ethyl-γ-butyrolactone was used instead of α-ethyl-γ-butyrolactone.
The reduction decomposition potential and the potential window were measured.

Example 3 An electrolytic solution was prepared in the same manner as in Example 1 except that γ-ethyl-γ-butyrolactone was used instead of α-ethyl-γ-butyrolactone.
The reduction decomposition potential and the potential window were measured.

(Example 4) In the same manner as in Example 1 except that α-ethyl-γ-butyrolactone was used instead of α-ethyl-γ-butyrolactone, and a mixture of 60% by weight of α-ethyl-γ-butyrolactone and 40% by weight of propylene carbonate was used. Prepare the liquid,
The oxidation decomposition potential, reduction decomposition potential, and potential window were measured.

Example 5 An electrolytic solution was prepared in the same manner as in Example 1 except that α, β-diethyl-γ-butyrolactone was used instead of α-ethyl-γ-butyrolactone. And the potential window was measured.

Example 6 An electrolytic solution was prepared in the same manner as in Example 1 except that α-ethyl-β-methyl-γ-butyrolactone was used instead of α-ethyl-γ-butyrolactone. The decomposition potential and the potential window were measured.

(Comparative Example 1) An electrolytic solution was prepared in the same manner as in Example 1 using propylene carbonate instead of α-ethyl-γ-butyrolactone, and the oxidative decomposition potential, reductive decomposition potential, and potential window were measured. Was.

Comparative Example 2 Example 1 using γ-butyrolactone instead of α-ethyl-γ-butyrolactone
An electrolytic solution was prepared in the same manner as described above, and the oxidative decomposition potential, reductive decomposition potential, and potential window were measured.

Table 1 shows the results.

[0027]

As is apparent from Table 1, Examples 1, 2, 3, and 3 containing the γ-butyrolactone derivative of the present invention are shown.
4, 5, and 6 have a wider withstand voltage than the electrolyte solutions of Comparative Examples 1 and 2, and thus have a higher withstand voltage. Therefore, when used for an electric double layer capacitor, a capacitor having a large capacity can be obtained.

[0029]

According to the present invention, the above-mentioned problems have been solved and an electrolytic solution for an electric double layer capacitor having a high withstand voltage and a large electric double layer capacitor using the same can be provided.

Claims (3)

[Claims] 1. An electrolytic solution for an electric double layer capacitor, comprising an organic solvent-based electrolytic solution in which an electrolyte salt is dissolved in an organic solvent, wherein the organic solvent contains a derivative of γ-butyrolactone. 2. The electric double layer capacitor according to claim 1, wherein the γ-butyrolactone derivative has at least one ethyl group at the α-position, β-position or γ-position carbon on the lactone ring. Electrolyte. 3. An electric double-layer capacitor using the electrolytic solution according to claim 1 or 2.