JPH0246714A - Electrolyte for electrolytic capacitor - Google Patents

Abstract

PURPOSE:To improve a solubility of a solvent in response to an increase in the frequency of a switching power supply and a reduction in the size of an electrolytic capacitor and moreover, to enable a high conductance by a method wherein sulfonium salt is used as a solute. CONSTITUTION:An electrolytic solution consists of a solution obtainable by deissolving sulfonium salt, which is used as a solute, into an aprotic solvent. The cationic component of the solute is sulfonium ions which are represented by formulas I-IV. In the above formulas, R1-R4 show an alkyl groups or an aryl group having a number of carbons of 1-10. Moreover, in alicylic sulfonium, ions, which are represented by the formula II, and polycation, which is represented by the formulas III and IV, (l) is generally 4-6 and (m) is generally 1-10. The anionic component of the solute is chosen from among a carboxylic acid and phenol and the like, a boric acid, a phosphoric acid, a phosphorus acid, a carbonic acid, a silinic acid and their derivatives, a picric acid and a sulfonic acid, a nitric acid, a sulfuric acid, a sulfurous acid, a thiocyanic acid and their derivatives and a very strong acid containing halogen atoms.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrolytic solution for an electrolytic capacitor (hereinafter sometimes simply referred to as an electrolytic solution). Specifically, the present invention relates to an electrolytic solution using a novel solute containing sulfonium ions.

The characteristics of an electrolytic capacitor are determined by various factors, but the characteristics of the electrolyte that is housed in the outer case together with the capacitor element have a particularly large effect on impedance or equal series resistance (ESR). It turns out that this is true.

For example, electrolytic capacitors have traditionally used ethylene glycol-ammonium adipate-based electrolytes. Furthermore, for low pressure applications, an electrolytic solution is used in which an amine salt of phthalic acid or maleic acid is dissolved in a solvent such as N,N-dimethylformamide or γ-butyrolactone. However, as the impedance of electrolytic capacitors has become lower in recent years, the above electrolytes are not sufficient, and there is a need for electrolytes that have even higher conductivity and can be used for long periods of time at temperatures exceeding 100°C. Therefore, electrolytes containing various quaternary ammonium salts or quaternary phosphonium salts as solutes have been proposed. (Unexamined Japanese Patent Publication No. 62-1
8018, 62-145713-6, 62-15
6810. 62-272510-3, 63-101
On the other hand, as electronic equipment becomes more sophisticated and more compact, there is an increasing demand for high-performance electrolytic capacitors, such as higher frequencies for switching power supplies and smaller electrolytic capacitors. Therefore, there is a need for new solutes that have good solubility in solvents and exhibit even higher electrical conductivity.

In order to solve the problem, the present inventors conducted intensive studies in order to find a new IIt solution with even higher conductivity, and found that a sulfonium salt using sulfur with a large ionic radius as the central element of the cation was developed. The present invention was completed by discovering that this material has better solubility and higher electrical conductivity than quaternary ammonium and phosphonium salts such as carbon and phosphorus.

That is, the present invention provides an electrolytic solution for an electrolytic capacitor characterized by using a sulfonium salt as a solute.

The electrolyte used in the present invention consists of a sulfonium salt dissolved in an aprotic solvent.

The cation component of the solute is a sulfonium ion represented by the following general formulas (1) to (IV).

In the above formula, R1-R4 represent an alkyl group having 1 to 10 carbon atoms or an aryl group, but generally, methyl,
These include ethyl, propyl, butyl, phenyl and benzyl groups. Furthermore, in the alicyclic sulfonium ion represented by the general formula (n) and the polycation represented by the general formulas (I[I) and (IV), l is 4 to 6 and m is 1 to
10 is common.

Specific sulfonium ions applicable to general formula (1) include trimethylsulfonium, triethylsulfonium, tripropylsulfonium, tributylsulfonium, methyldiethylsulfonium, methyldipropylsulfonium, methyldibutylsulfonium, dimethylethylsulfonium, dimethylpropylsulfonium,
Dimethylbutylsulfonium, ethyldipropylsulfonium, ethyldibutylsulfonium, diethylpropylsulfonium, diethylbutylsulfonium, propyldibutylsulfonium, dipropylbutylsulfonium, dimethylphenylsulfonium, diethylphenylsulfonium, dipropylphenylsulfonium, dibutylphenylsulfonium, methyldiphenylsulfonium , ethyldiphenylsulfonium, propyldiphenylsulfonium, butyldiphenylsulfonium, triphenylsulfonium, dimethylbenzylsulfonium, and the like.

Among the sulfonium ions mentioned above, when you want to obtain an electrolyte with high conductivity, sulfonium ions with a small molecular weight,
For example, trimethylsulfonium, dimethylethylsulfonium, methyldiethylsulfonium ions, etc. are preferred, but when it is desired to obtain an electrolytic solution with high pressure resistance, sulfonium ions with high molecular weights, such as tributylsulfonium, trihexylsulfonium ions, etc. are preferred.

The anion component of the solute is a conjugate base of an acid selected from the following five groups.

(11 carboxylic acids and phenols (2) boric acid, phosphoric acid, phosphorous acid, hypophosphorous acid, carbonic acid,
Silicic acid and their derivatives [3] Picric acid and sulfonic acid (4) Nitric acid, sulfuric acid, sulfite, thiocyanic acid and their derivatives (5) Very strong acids containing halogen atoms (1) and (
The anion selected from the group 2) is good″fi
1 m-forming anion", and can be used not only for low voltage capacitors but also for medium and high voltage capacitors.Those selected from (3), (41) and (5) also have oxide film forming ability. , strongly acidic;
Since it tends to corrode the oxide film, it can only be used with low voltage capacitors of 100V or less. In particular, the anion selected from (5) liberates halide ions that are unfavorable to aluminum, so it can only be used in low-voltage capacitors of 10 V or less.

Group (1) carboxylic acids have a total carbon number of 1 to 30
aliphatic and aromatic mono- or polyhydric carboxylic acids.

Specifically, formic acid, acetic acid, propionic acid, butyric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, stearic acid, nonadecanoic acid, Araxic acid, isobutyric acid, isovaleric acid, isocaproic acid, ethylbutyric acid, methylvaleric acid, isocaprylic acid, propylvaleric acid, ethylcaproic acid, isocapric acid, labelculostearic acid, pivalic acid, 2,2-dimethylbutanoic acid, 2.2-dimethylpentanoic acid, 2,2-dimethylhexanoic acid, 2.2-dimethylhebutanoic acid, 2.
2-dimethyloctanoic acid, 2-methyl-2-ethylbutanoic acid, 2-methyl-2-ethylpentanoic acid, 2-methyl-2-ethylhexanoic acid, 2-methyl-2-ethylheptanoic acid, 2-methyl- 2-propylpentanoic acid, 2-
Methyl-2-propylhexanoic acid, 2-methyl-2-propylhebutanoic acid, acrylic acid, crotonic acid, isocrotonic acid, 3-butenoic acid, pentenoic acid, hexenoic acid, heptenoic acid, octenoic acid, nonenoic acid, decenoic acid , undecenoic acid, dodecenoic acid, tuzuic acid, fisteric acid, goshuylic acid, palmitoleic acid, petroselinic acid, oleic acid, elaidic acid, vaccenic acid, gadoleic acid, methacrylic acid, 3-methylcrotonic acid, tiglic acid, methylpentenoic acid, Aliphatic monocarboxylic acids such as cyclopentanecarboxylic acid and cyclohexanecarboxylic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, speric acid, azelaic acid, sebacic acid, undecanoic acid, dodecanedioic acid, Tridecane dioic acid, tetradecanedioic acid, pentadecanoic acid, hexadecanedioic acid, heptatecandioic acid, octadecadiene, nonadecanoic acid, eicosandioic acid, methylmalonic acid, ethylmalonic acid, propylmalonic acid, butylmalonic acid, pentylmalonic acid, hexyl Malonic acid, dimethylmalonic acid, methylethylmalonic acid, diethylmalonic acid, methylpropylmalonic acid, methylbutylmalonic acid, ethylpropylmalonic acid, dipropylmalonic acid, ethylbutylmalonic acid, propylbutylmalonic acid, dibutylmalonic acid, Methylsuccinic acid, ethylsuccinic acid, 2
．． 2-dimethylsuccinic acid, 2,3-dimethylsuccinic acid,
2-methylglutaric acid, 3-methylglutaric acid, 3-methyl-3-ethylglutaric acid, 3,3-diethylglutaric acid, maleic acid, citraconic acid, 1.5-octanedicarboxylic acid, 5.6-decanedicarboxylic acid acid, 1,7-decanedicarboxylic acid, 4,6-dimethyl-4-nonene-1
, 2-dicarboxylic acid, 4,6-dithymer-1,2-nonanedicarboxylic acid, 1,7-dodecanedicarboxylic acid, 5-
Ethyl-1,1O-decanedicarboxylic acid, 6-methyl-
6-dodecene-1,12-dicarboxylic acid, 6-methyl-
1,12-dodecanedicarboxylic acid, 6-ethylene-1,
12-dodecanedicarboxylic acid, 6-ethyl-1,12-
Dodecanedicarboxylic acid, 7-methyl-7-tetradecene-1,14-dicarboxylic acid, 7-methyl-1,14-tetradecanedicarboxylic acid, 3-hexyl-4-decene-
1,2-dicarboxylic acid, 3-hexyl-1,2-decanedicarboxylic acid, 6-ethylene-9-hexadecene-1,
16-dicarboxylic acid, 6-ethyl-1,16-hexadecanedicarboxylic acid, 6-phenyl-1,12-dodecanedicarboxylic acid, 7゜12-dimethyl-7,11-octadecadiene-1,18-dicarboxylic acid, 7,12-dimethyl-1,18-octadecanedicarboxylic acid, 6,8-
diphenyl-1,14-tetradecanedicarboxylic acid, 1
, 1-cyclopentanedicarboxylic acid, 1,2-cyclopenkunedicarboxylic acid, 1.1-cyclohexanedicarboxylic acid, 1.2-cyclohexanedicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, 5-norbornene-2 , aliphatic dicarboxylic acids such as 3-dicarboxylic acid, benzoic acid, toluic acid, ethylbenzoic acid, propylbenzoic acid, isopropylbenzoic acid, butylbenzoic acid, isobutylbenzoic acid, nibutylbenzoic acid, tertiary butylbenzoic acid,
Hydroxybenzoic acid, anisic acid, ethoxybenzoic acid, propoxybenzoic acid, isopropoxybenzoic acid, butoxybenzoic acid, isobutoxybenzoic acid, sec-butoxybenzoic acid, tertiary-butoxybenzoic acid, aminobenzoic acid, N-methylaminobenzoic acid , N-ethylaminobenzoic acid, N-propylaminobenzoic acid, N-isopropylaminobenzoic acid, N-butylaminobenzoic acid, N-isobutylaminobenzoic acid, N-sec-butylaminobenzoic acid, N-tert-butyl Aromatic monocarboxylic acids (o, m, p
- Aromatic polyvalent carboxylic acids such as isophthalic acid, terephthalic acid, 3-nitrophthalic acid, 4-nitrophthalic acid, trimellitic acid, hemimellitic acid, trimesic acid, and pyromellitic acid. I can give an example.

Specific examples of phenols include phenol, catechol, resorcinol, hydroquinone, phloroglucinol, pyrogallol, 1,2.4-)lyhydroxybenzene, 0-nitrophenol, m-nitrophenol, and p-nitrophenol. , 2.4-dinitrophenol, 2.5-dinitrophenol, 2,6-dinitrophenol, 3.4-dinitrophenol, 4-nitrocatechol, and 2-nitroresorcinol.

Those belonging to group (2) include boric acid, the following general formula (
Boric acid derivatives represented by V), phosphoric acid, and the following general formula (V
Phosphoric acid ester represented by l), phosphorous acid, phosphorous acid derivative represented by the following general formula (■), hypophosphorous acid, hypophosphorous acid derivative represented by the following general formula (■), carbonic acid, the following It is a carbonic acid monoester and silicic acid represented by the general formula (IX).

R60-P-OH(Vl) OR? R6-P-OH (■) R7 R6-P-OH (■) R-ReOCOH (IX) In the formula C, R6-R8 represents an alkyl group or an aryl group having 1 to 10 carbon atoms. Further, one of R6 or R1 may be a hydrogen atom. ] Specific examples of the boric acid derivative represented by (V) include methylboric acid, ethylboric acid, phenylboric acid, and the like.

Specific examples of the phosphoric acid ester represented by formula (Vl) include monomethyl phosphoric acid, dimethyl phosphoric acid, phenyl phosphoric acid, and the like.

Specific examples of the phosphorous acid derivative represented by formula (■) include phosphorous acid monomethyl ester, methylphosphonic acid, methylphosphonic acid methyl ester, etc. Examples include methylphosphinic acid, dimethylphosphinic acid, phenylphosphinic acid, etc. Can be done.

Specific examples of the carbonate monoester represented by (IX) include carbonate monomethyl ester, carbonate monophenyl ester, and the like.

Those belonging to group (3) are picric acid and aliphatic and aromatic monovalent or polyvalent sulfonic acids having a total carbon number of 1 to 30.

Specifically, methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, butanesulfonic acid, pentanesulfonic acid, hexanesulfonic acid, heptanesulfonic acid, octanesulfonic acid, nonanesulfonic acid, decanesulfonic acid, vinylsulfonic acid, allyl Sulfonic acid, 1,2-ethanedisulfonic acid, R4-butanedisulfonic acid, benzenesulfonic acid, p~toluenesulfonic acid, 1-ethylbenzenesulfonic acid, xylene sulfonic acid, naphthalenesulfonic acid, phenolsulfonic acid, nitrobenzenesulfonic acid, 2I4 Examples include -dinitrobenzenesulfonic acid, picrylsulfonic acid, pyridine-3-sulfonic acid, m-benzenesulfonic acid, and toluene-3,4-disulfonic acid.

Those belonging to group (4) include nitric acid, sulfuric acid, sulfuric acid monoester represented by the following general formula (X), sulfite, and sulfite monoester represented by the following general formula (XI).
H(XI) (In the formula, R9 represents an alkyl group or aryl group having 1 to 10 carbon atoms.) Those belonging to group (5) contain a halogen atom with high electronegativity, so they are extremely acidic. It is an acid that shows

Specifically, HBF*, HPF61 HAsF, , ,
HSbF6.

ChSOJ, ChCOzH, C4F9SO3H,C
4F*COJ.

An example is HC104.

As a solvent for dissolving the sulfonium salt of the present invention, N
-Methylformamide, N-ethylformamide, N
, N-dimethylformamide, N,N-diethylformamide, N-methylacetamide.

N-ethylacetamide, N,N-dimethylacetamide, N,N-diethylacetamide, N-methylpyrrolidinone, N-methyloxazolidinone.

Amide solvents such as N,N'-dimethylimidazolidinone, γ-butyrolactone, γ-valerolactone.

Lactone solvents such as δ-valerolactone, carbonate solvents such as ethylene carbonate, propylene carbonate, butylene carbonate, and nitrile solvents such as 3-methoxypropionitrile.

Examples include phosphoric acid ester solvents such as trimethyl phosphate and the like alone or in combination.

Among these, an electrolytic solution containing T-butyrolactone as a main medium is preferred because it has a wide usable temperature range, low toxicity, and strong halogen resistance.

The amount of the sulfonium salt dissolved in the above solvent varies depending on the desired conductivity and spark voltage, but is generally below the saturation concentration, preferably from 0.1 to 40% by weight. More preferably 5 to 30% by weight for low voltage capacitors.
For medium and high voltage capacitors, it is 1 to 20% by weight.

The electrolytic solution of the present invention essentially consists of a sulfonium salt and an aprotic solvent, but it has the following properties: prevention of galvanic corrosion, reduction of leakage current, etc.
Small amounts of co-solutes may be added for various purposes.

The sulfonium salt used as a solute in the present invention has good solubility in a solvent, and its electrolyte exhibits high conductivity and can be used in conjunction with a solvent that is in a liquid state over a wide temperature range. This is an electrolytic solution for electrolytic capacitors that has a wide temperature range.

EXAMPLES The present invention will be explained in more detail with reference to Examples and Comparative Examples below.

Example 1 An electrolytic solution was obtained by dissolving 20% by weight of monotrimethylsulfonium maleate in a γ-butyrolactone solvent. The conductivity of this electrolyte at 25°C is 14.4 mS/a
m, and 5 rt on + and -1 set of aluminum smooth foils.
(The spark generation voltage when applying a constant current of A7cm" was 85V.

Example 2 In Example 1, N, instead of γ-butyrolactone,
The conductivity and spark voltage of the electrolyte when N-dimethylformamide was used were 22.0 mS/cm, respectively.

It was 50V.

Example 3 In Example 1, when monotrimethylsulfonium phthalate was used instead of monotrimethylsulfonium maleate, the conductivity and spark voltage of the electrolyte were 1, respectively.
It was 1.3 mS/cm and 94 V.

Example 4 In Example 3, N, instead of T-butyrolactone,
The conductivity and spark voltage of the electrolyte when N-dimethylformamide was used were each 16.4 mS/cm.

It was 50V.

Example 5 In Example 3, when propylene carbonate was used instead of γ-butyrolactone, the conductivity of the electrolyte and the spark voltage were 8.5 mS7cm, respectively.

It was 96V.

Example 6 In Example 1, when trimethylsulfonium borohydride was used instead of monotrimethylsulfonium maleate, the conductivity of the electrolyte and the spark voltage were 20.0 mS/c+++ and 76 V, respectively. .

Example 7 In Example 1, when mono(methyltetramethylenesulfonium) maleate was used instead of monotrimethylsulfonium maleate, the conductivity and spark voltage of the electrolytic solution were each 10.4 mS/cm.

It was 84V.

Claims (1)

[Claims] An electrolytic solution for electrolytic capacitors characterized by using a sulfonium salt as a solute.