JP2012129270A - Electrolytic solution for electric double layer capacitor and electric double layer capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolytic solution for an electric double layer capacitor, high in withstand voltage characteristics, and an electric double layer capacitor.SOLUTION: In an electrolytic solution for an electric double layer capacitor, a compound such as tetrafluoroboric acid spiro-(1,1')-bipiperidinium is dissolved in a solvent as an electrolyte. The electrolytic solution for an electric double layer capacitor includes a salt comprising a cation of alkyl quaternary ammonium, ammonium having a spiro structure, alkyl imidazolium or alkyl imidazolinium, and an anion of a boron compound ion having a specific structure.

Description

  The present invention relates to an electrolytic solution for an electric double layer capacitor and an electric double layer capacitor having high pressure resistance.

  In recent years, electrochemical capacitors such as electric double layer capacitors and electrolytic capacitors have been used in a wide range of applications as a memory backup power source for electronic devices and electric devices, and as a memory backup for telephones, mobile phones, AV devices and the like. Yes.

  An electric double layer capacitor is a charge storage device using an electric double layer formed at the interface between a polarizable electrode and an electrolyte.

  The electrolytic solution used for the electric double layer capacitor has a drawback that when the conductivity is low, the internal resistance of the capacitor increases, and there is a disadvantage that the voltage drops during charging and discharging.

  Also, if the electrolyte concentration in the electrolyte solution is low and the amount of ions is insufficient, the internal resistance increases during charging at a large current density, and therefore it is desirable that the electrolyte concentration in the electrolyte solution be as high as possible.

  Conventionally, as an electrolytic solution for an electric double layer capacitor, an aprotic solvent such as γ-butyrolactone (hereinafter abbreviated as “GBL”), propylene carbonate (hereinafter abbreviated as “PC”) or the like is used. A solution in which an electrolyte composed of a quaternary onium salt is dissolved is known.

  However, as disclosed in Patent Document 1 or 2, the electric double layer capacitor using the solvent described in the preceding paragraph as a solvent has a solvent caused by the influence of halides generated from moisture derived from activated carbon electrodes or application of high voltage. It has become a problem that it decomposes and leads to expansion of the capacitor due to gas generation and deterioration of life characteristics.

JP 2009-302121 A JP 2010-1111597 A

  An object of the present invention is to provide an electrolytic solution for an electric double layer capacitor and an electric double layer capacitor having high pressure resistance.

  In view of the said subject, as a result of intensive studies, the present inventors have expressed the general formulas (2) to (5) in the electrolytic solution for an electric double layer capacitor in which the compound represented by the general formula (1) is dissolved. The present inventors have found that an electrolytic solution for an electric double layer capacitor containing a boron compound salt and an electric double layer capacitor using the same can solve the above problems, and have completed the present invention.

  A first invention is an electrolytic solution for an electric double layer capacitor in which a compound represented by the following general formula (1) is dissolved in an organic solvent, and a boron compound salt represented by the following general formulas (2) to (5) Any one of these is contained, The electrolyte solution for electric double layer capacitors characterized by the above-mentioned.

（式（１）中、Ａは、アルキル第四級アンモニウム、スピロ構造を有するアンモニウム、アルキルイミダゾリウム、アルキルイミダゾリニウムである。Ｘ⁻はアニオンを示す。）

(In Formula (1), A is alkyl quaternary ammonium, ammonium which has a spiro structure, alkyl imidazolium, and alkyl imidazolinium. X < ^- > shows an anion.)

（式（２）中、Ｒ_１〜Ｒ_４は、それぞれ同一でも異なっていてもよい水素原子、炭素数１〜４のアルキル基、ハロゲン原子、ニトロ基、フルオロアルキル基、アリール基を表す。Ａは、アルキル第四級アンモニウム、スピロ構造を有するアンモニウム、アルキルイミダゾリウム、アルキルイミダゾリニウムである。）

(In Formula (2), R < ₁ > -R < ₄ > represents the hydrogen atom which may be same or different, respectively, a C1-C4 alkyl group, a halogen atom, a nitro group, a fluoroalkyl group, and an aryl group. Are alkyl quaternary ammonium, ammonium having a spiro structure, alkyl imidazolium, and alkyl imidazolinium.)

（式（３）中、Ｒ_５、Ｒ_６は、それぞれ同一でも異なっていてもよい水素原子、炭素数１〜４のアルキル基、ハロゲン原子、ニトロ基、フルオロアルキル基、アリール基を表す。Ａは、アルキル第四級アンモニウム、スピロ構造を有するアンモニウム、アルキルイミダゾリウム、アルキルイミダゾリニウムである。）

(In formula (3), R ₅ and R ₆ each represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a halogen atom, a nitro group, a fluoroalkyl group, or an aryl group, which may be the same or different. Are alkyl quaternary ammonium, ammonium having a spiro structure, alkyl imidazolium, and alkyl imidazolinium.)

（式（４）中、Ｒ_７、Ｒ_８は、それぞれ同一でも異なっていてもよい水素原子、炭素数１〜４のアルキル基、ハロゲン原子、ニトロ基、フルオロアルキル基、アリール基を表す。Ａは、アルキル第四級アンモニウム、スピロ構造を有するアンモニウム、アルキルイミダゾリウム、アルキルイミダゾリニウムである。）

(In Formula (4), R <_7> , R < ₈ > represents the hydrogen atom which may be same or different, respectively, a C1-C4 alkyl group, a halogen atom, a nitro group, a fluoroalkyl group, and an aryl group. Are alkyl quaternary ammonium, ammonium having a spiro structure, alkyl imidazolium, and alkyl imidazolinium.)

（式（５）中、Ａは、アルキル第四級アンモニウム、スピロ構造を有するアンモニウム、アルキルイミダゾリウム、アルキルイミダゾリニウムである。）

(In the formula (5), A represents alkyl quaternary ammonium, ammonium having a spiro structure, alkyl imidazolium, or alkyl imidazolinium.)

  2nd invention is 0.01-30 mass% of content of boron compound salt in the electrolyte solution for electrical double layer capacitors, The electrical double layer capacitor as described in 1st invention characterized by the above-mentioned Electrolytic solution.

  3rd invention is the electrical double layer capacitor produced using the electrolyte solution for electrical double layer capacitors as described in 1st or 2nd invention.

  INDUSTRIAL APPLICABILITY The present invention can provide an electrolytic solution for an electric double layer capacitor and an electric double layer capacitor that have high electrical conductivity and high pressure resistance.

  Hereinafter, the electrolytic solution for the electric double layer capacitor and the electric double layer capacitor will be described in detail.

  The present invention provides a boron compound salt represented by the following general formulas (2) to (5) in an electrolytic solution for an electric double layer capacitor in which a compound represented by the following general formula (1) is dissolved in an organic solvent. Any one of these is contained, The electrolyte solution for electric double layer capacitors characterized by the above-mentioned.

  In the general formula (1), examples of A include alkyl quaternary ammonium, ammonium having a spiro structure, alkyl imidazolium, and alkyl imidazolinium.

  Examples of the alkyl quaternary ammonium include tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, dimethyldiethylammonium, dimethyldibutylammonium, methyltriethylammonium, methyltripropylammonium, methyltributylammonium and the like.

  Examples of ammonium having a spiro structure include azacyclobutane-1-spiro-1′-azacyclobutyl, pyrrolidine-1-spiro-1′-azacyclobutyl, spiro- (1,1 ′)-bipyrrolidinium, piperidine-1- Spiro-1′-pyrrolidinium, spiro- (1,1 ′)-bipiperidinium, 3-ethylpyrrolidinium-1-spiro-1′-pyrrolidinium, 3-ethylpyrrolidinium-1-spiro-1 ′-(3 '-Ethyl) pyrrolidinium, 2,4-difluoropyrrolidinium-1-spiro-1'-pyrrolidinium, 2,4-difluoropyrrolidinium-1-spiro-1'-(2 ', 4'-difluoro) pyrrolidinium Etc.

  Examples of the alkyl imidazolium include 1,3-dimethylimidazolium, 1,3-diethylimidazolium, 1-ethyl-3-methylimidazolium, 1,2,3-trimethylimidazolium, 1,2,3,4- Tetramethylimidazolium, 1,3-dimethyl-2-ethylimidazolium, 1,2-dimethyl-3-ethyl-imidazolium, 1,2,3-triethylimidazolium, 1,2,3,4-tetraethylimidazolium Lithium, 1,3-dimethyl-2-phenylimidazolium, 1,3-dimethyl-2-benzylimidazolium, 1-benzyl-2,3-dimethyl-imidazolium, 4-cyano-1,2,3-trimethyl Imidazolium, 3-cyanomethyl-1,2-dimethylimidazolium, 2-cyanomethyl-1,3-dimethyl-i Dazolium, 4-acetyl-1,2,3-trimethylimidazolium, 3-acetylmethyl-1,2-dimethylimidazolium, 4-methylcarbooxymethyl-1,2,3-trimethylimidazolium, 3-methylcarbo Oxymethyl-1,2-dimethylimidazolium, 4-methoxy-1,2,3-trimethylimidazolium, 3-methoxymethyl-1,2-dimethylimidazolium, 4-formyl-1,2,3-trimethylimidazolium Rium, 3-formylmethyl-1,2-dimethylimidazolium, 3-hydroxyethyl-1,2-dimethylimidazolium, 4-hydroxymethyl-1,2,3-trimethylimidazolium, 2-hydroxyethyl-1, 3-dimethylimidazolium etc. are mentioned.

  Examples of the alkyl imidazolinium include 1,2,3,4-tetramethylimidazolinium, 1,3,4-trimethyl-2-ethylimidazolinium, and 1,3-dimethyl-2,4-diethylimidazolinium. 1,2-dimethyl-3,4-diethylimidazolinium, 1-methyl-2,3,4-triethylimidazolinium, 1,2,3,4-tetraethylimidazolinium, 1,2,3- Trimethylimidazolinium, 1,3-dimethyl-2-ethylimidazolinium, 1-ethyl-2,3-dimethylimidazolinium, 1,2,3-triethylimidazolinium, 4-cyano-1,2, 3-trimethylimidazolinium, 3-cyanomethyl-1,2-dimethylimidazolinium, 2-cyanomethyl-1,3-dimethylimidazolinium, 4- Cetyl-1,2,3-trimethylimidazolinium, 3-acetylmethyl-1,2-dimethylimidazolinium, 4-methylcarbooxymethyl-1,2,3-trimethylimidazolinium, 3-methylcarbooxy Methyl-1,2-dimethylimidazolinium, 4-methoxy-1,2,3-trimethylimidazolinium, 3-methoxymethyl-1,2-dimethylimidazolinium, 4-formyl-1,2,3- Trimethylimidazolinium, 3-formylmethyl-1,2-dimethylimidazolinium, 3-hydroxyethyl-1,2-dimethylimidazolinium, 4-hydroxymethyl-1,2,3-trimethylimidazolinium, 2 -Hydroxyethyl-1,3-dimethylimidazolinium etc. are mentioned.

In general formula (1), X ⁻ includes hexafluorophosphate ion (PF ₆ ⁻ ), hexafluoroantimonate ion (SbF ₆ ⁻ ), tetrafluoroborate ion (BF ₄ ⁻ ), and trifluoromethanesulfonate ion. (CF ₃ SO ₃ ⁻ ), trifluoroacetate ion (CF ₃ CO ₂ ⁻ ), bistrifluoromethanesulfonyl imido ion ((CF ₃ SO ₂ ) ₂ N ⁻ ), perfluorobutane sulfonate ion (C ₄ F ₉ SO ₃ ^-), tris trifluoromethane sulfonyl methide acid ion _{((CF 3 SO 2) 3} C -) can be mentioned, tetrafluoroborate ion (BF ₄ ^-), among others preferred.

  Specific examples of the general formula (1) include the following compounds (a) to (c).

  Examples of the organic solvent include cyclic carbonate ester, chain carbonate ester, phosphate ester, cyclic ether, chain ether, lactone compound, chain ester, nitrile compound, amide compound, sulfone compound and the like.

Examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, butylene carbonate, 4-fluoro-1,3-dioxolan-2-one, 4- (trifluoromethyl) -1,3-dioxolan-2-one, and the like. Preferably, ethylene carbonate and propylene carbonate are used.
Examples of chain carbonates include dimethyl carbonate, ethyl methyl carbonate, methyl n-propyl carbonate, methyl isopropyl carbonate, n-butyl methyl carbonate, diethyl carbonate, ethyl n-propyl carbonate, ethyl isopropyl carbonate, n-butyl ethyl carbonate, di- Examples include n-propyl carbonate, diisopropyl carbonate, di n-butyl carbonate, fluoroethyl methyl carbonate, difluoroethyl methyl carbonate, trifluoroethyl methyl carbonate, and preferably dimethyl carbonate and ethyl methyl carbonate.
Examples of the phosphate ester include trimethyl phosphate, triethyl phosphate, ethyldimethyl phosphate, diethylmethyl phosphate, and the like.
Examples of the cyclic ether include tetrahydrofuran and 2-methyltetrahydrofuran.
Examples of the chain ether include dimethoxyethane.
Examples of the lactone compound include γ-butyrolactone and γ-valerolactone.
Examples of chain esters include methyl formate, methyl acetate, ethyl acetate, and methyl propionate.
Examples of the nitrile compound include acetonitrile.
Examples of the amide compound include dimethylformamide and diethylformamide.
Examples of the sulfone compound include sulfolane, methyl sulfolane, and ethyl sulfolane.
Of these, preferred are cyclic carbonates, chain carbonates, lactone compounds, and sulfone compounds. These solvents may be used alone or in combination of two or more.

  The boron compound salt is a compound represented by the following general formulas (2) to (5).

In General Formula (2), R _{1 to} R ₄ each represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a halogen atom, a nitro group, a fluoroalkyl group, or an aryl group, which may be the same or different. A is alkyl quaternary ammonium, ammonium having a spiro structure, alkyl imidazolium, or alkyl imidazolinium.

In General Formula (3), R ₅ and R ₆ each represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a halogen atom, a nitro group, a fluoroalkyl group, or an aryl group, which may be the same or different. A is alkyl quaternary ammonium, ammonium having a spiro structure, alkyl imidazolium, or alkyl imidazolinium.

In general formula (4), R <_7> , R < ₈ > represents the hydrogen atom which may be same or different, respectively, a C1-C4 alkyl group, a halogen atom, a nitro group, a fluoroalkyl group, and an aryl group. A is alkyl quaternary ammonium, ammonium having a spiro structure, alkyl imidazolium, or alkyl imidazolinium.

  In general formula (5), A is alkyl quaternary ammonium, alkyl quaternary ammonium, ammonium having a spiro structure, alkyl imidazolium, and alkyl imidazolinium.

  A in the general formulas (2) to (5) is the same as A in the general formula (1).

  Specific examples of the boron compound salts represented by the general formulas (2) to (5) include the following compounds (ke) to (v).

0.01-40 mass% is preferable and, as for content of the electrolyte in the electrolyte solution for electrical double layer capacitors, 0.1-30 mass% is mentioned more preferably.
The content of the boron compound salt represented by the general formulas (2) to (5) in the electrolytic solution for an electric double layer capacitor is preferably 0.01 to 30% by mass, more preferably 0.1 to 20% by mass, 0.5-2 mass% is particularly preferable.

  By adding the boron compound salt of the present invention, it is possible to reduce the effect of capacitor deterioration due to hydrogen halide (HF or the like) in the electrolytic solution, to prevent coloring due to hydrogen halide, The breakdown voltage of the multilayer capacitor can be improved.

The content of water in the electrolytic solution for electric double layer capacitors is preferably as small as possible, and the water content is preferably 100 ppm or less, more preferably 50 ppm or less, and particularly preferably 10 ppm or less from the viewpoint of electrochemical stability.
If it exceeds 100 ppm, there is a drawback that the electrical characteristics of the capacitor are degraded.

  The electric double layer capacitor of the present invention is produced by impregnating the polarizable electrode of the capacitor with the electrolyte for electric double layer capacitor of the present invention as a driving electrolyte.

  As the polarizable electrode, carbon materials such as activated carbon powder and activated carbon fibers, noble metal oxide materials, conductive polymer materials, and the like can be used.

  The electric double layer capacitor of the present invention can be obtained by sandwiching a separator between two polarizable electrodes and impregnating the electrolytic solution for the electric double layer capacitor of the present invention and then storing the separator in a stainless outer case. .

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

  Examples of the aluminum electrolytic capacitor include a coin type, a wound type, and a rectangular type. The electrolytic solution of the present invention can be applied to any aluminum electrolytic capacitor.

  Hereinafter, the present invention will be described more specifically with reference to examples. The present invention is not limited in any way by the examples.

Example 1
Using propylene carbonate as the solvent, adjusting the electrolyte (ke) to 0.1% by mass as the electrolyte, 26% by mass of spiro- (1,1 ′)-bipiperidinium tetrafluoroborate as the boron compound salt, An electrolytic solution for an electric double layer capacitor was obtained. Table 1 shows measured values of the conductivity of the electrolyte at temperatures of -40 ° C and 30 ° C.

As a polarizable electrode, 90% by mass of activated carbon powder (particle size 20 μm, specific surface area 2000 m ² / g) and 10% by mass of polytetrafluoroethylene powder were kneaded and rolled with a roll to prepare a sheet having a thickness of 0.4 mm. This sheet was punched out to a diameter of 13 mmφ to obtain a disk electrode.

  A polypropylene separator is sandwiched between the two disc-shaped electrodes, the previously prepared electrolyte is vacuum impregnated, and then the electrode is placed on a stainless steel case, and then a stainless steel lid is integrated via a gasket. The coin-type electric double layer capacitor having a rating of 3.3 V and a capacitance of 1.5 F was produced.

  The obtained electric double layer capacitor was subjected to a withstand voltage test by applying 3.3 V for 1000 hours in a constant temperature bath at a temperature of 70 ° C. Table 1 shows the capacitance values after initial and withstand voltage tests and the rate of change (%) in capacitance. The capacitance of the electric double layer capacitor was obtained from a voltage gradient when charged at 1 mA after being charged at a voltage of 3.3 V for 1 hour.

(Examples 2 to 9, Comparative Example 1)
An electrolytic solution for an electric double layer capacitor and an electric double layer capacitor were prepared in the same manner as in Example 1, except that the compounds and contents corresponding to Table 1 were used instead of the compounds (examples) described in Example 1. The capacitor characteristics were evaluated.

  From Table 1, it was found that Examples 1 to 9 were superior in pressure resistance because the rate of decrease in capacitance was smaller.

  The electrolytic solution for an electric double layer capacitor and the electric double layer capacitor using the same of the present invention have excellent life characteristics, and can be used in a wide range of industrial fields from small electronic devices to large automobiles.

Claims (3)

In an electrolytic solution for an electric double layer capacitor in which a compound represented by the following general formula (1) is dissolved in an organic solvent, any one of boron compound salts represented by the following general formulas (2) to (5) An electrolytic solution for an electric double layer capacitor, comprising:

(In Formula (1), A is alkyl quaternary ammonium, ammonium which has a spiro structure, alkyl imidazolium, and alkyl imidazolinium. X < ^- > shows an anion.)

(In Formula (2), R < ₁ > -R < ₄ > represents the hydrogen atom which may be same or different, respectively, a C1-C4 alkyl group, a halogen atom, a nitro group, a fluoroalkyl group, and an aryl group. Are alkyl quaternary ammonium, ammonium having a spiro structure, alkyl imidazolium, and alkyl imidazolinium.)

(In formula (3), R ₅ and R ₆ each represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a halogen atom, a nitro group, a fluoroalkyl group, or an aryl group, which may be the same or different. Are alkyl quaternary ammonium, ammonium having a spiro structure, alkyl imidazolium, and alkyl imidazolinium.)

(In Formula (4), R <_7> , R < ₈ > represents the hydrogen atom which may be same or different, respectively, a C1-C4 alkyl group, a halogen atom, a nitro group, a fluoroalkyl group, and an aryl group. Are alkyl quaternary ammonium, ammonium having a spiro structure, alkyl imidazolium, and alkyl imidazolinium.)

(In the formula (5), A represents alkyl quaternary ammonium, ammonium having a spiro structure, alkyl imidazolium, or alkyl imidazolinium.)   2. The electrolytic solution for an electric double layer capacitor according to claim 1, wherein the content of the boron compound salt is 0.01 to 30% by mass in the electrolytic solution for an electric double layer capacitor.   The electric double layer capacitor produced using the electrolyte solution for electric double layer capacitors of Claim 1 or 2.