Electrolyte for electrolytic capacitors and electrolytic capacit

Details Electrolyte for electrolytic capacitors and electrolytic capacit Electrolyte for electrolytic capacitors and electrolytic capacit

1987-10-21

1989-04-11

Griffin, Donald A.

Electricity: electrical systems and devices

Electrolytic systems or devices

Liquid electrolytic capacitor

252 622, H01G 902

Patent

active

048211532

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

This invention relates to an electrolyte for use in electrolytic capacitors and also to an electrolytic capacitor using the electrolyte.


TECHNICAL BACKGROUND

A typical electrolyte for electrolytic capacitors which has been hitherto used is an electrolyte of an ionogen dissolved in ethylene glycol. However, this type of electrolyte has a low specific conductance and tends to cause an impedance characteristic to deteriorate. To avoid this, usual practice is to add water to the electrolyte, but such an electrolyte is elevated in vapor pressure at high temperatures and is apt to react with an aluminum electrode, thus being unsuitable for use in a high temperature range.
In order to improve the above drawbacks, there have been proposed an electrolyte using .gamma.-butyrolactone as a solvent and a triethylamine salt of phthalic acid as described in Japanese Laid-open patent application No. 61-70711 and an electrolyte an amine salt of maleic acid dissolved in a mixed solvent of .gamma.-butyrolactone and ethylene glycol as described in Japanese Laid-open patent application No. 54-7564.
Moreover, Japanese Laid-open patent application No. 59-78522 describes electrolytes using quaternary ammonium salts of linear dicarboxylic acids, and Japanese Laid-open patent application No. 61-93610 teaches electrolytes using tetralkylammonium salts of 1,10-decanedicarboxylic acid or 1,6-decanedicarboxylic acid.
However, the known electrolytes comprising triethylamine salts of phthalic acid or maleic acid dissolved in a .gamma.-butyrolactone solvent are disadvantageous in that the acid dissociation is caused by the proton equilibrium of the triethylamine, so that ions are produced only in small amounts. Thus, a sufficiently high specific conductance cannot be obtained. On the other hand, with electrolytes using the quaternary ammonium salts of linear dicarboxylic acids or the tetraalkylammonium salts of 1,10-decanedicarboxylic acid or 1,6-decanedicarboxylic acid, the specific conductance becomes low because of the rather inappropriate combination with the acid. Accordingly, electrolytic capacitors using these electrolytes cannot disadvantageously lower the impedance characteristic.


DISCLOSURE OF THE INVENTION

The present invention contemplates to provide an electrolyte for electrolytic capacitors and an electrolytic capacitor using the electrolyte in which a solute of the electrolyte used is a quaternary ammonium salt of either a carboxylic acid selected from the group consisting of phthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid and maleic acid, or an alkyl or nitro-substituted compound of the acid, whereby the resultant electrolytic capacitor has improved low temperature characteristics and improved characteristics with time at high temperatures, thus ensuring a prolonged life.


BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view illustrating the respective members of an electrolytic capacitor; and
FIGS. 2-4 are, respectively, graphs of characteristics, in relation to time, of aluminum electrolytic capacitors having ratings 10 V and 2200 .mu.F (.phi.16.times.32) and using known electrolytes and electrolytes of the invention, in which
FIG. 2 is a characteristic graph showing a variation in electrostatic capacity by application of a rated voltage,
FIG. 3 is a characteristic graph showing a variation in tangent of the loss angle by application of a rated voltage, and
FIG. 4 is a characteristic graph of a variation in leakage current in the absence of an applied voltage.
The following reference numerals are used in the drawings


BEST MODE FOR CARRYING OUT THE INVENTION

The present invention provides an electrolyte for use in an electrolytic capacitor which comprises a solution, in an organic solvent, of a quaternary ammonium salt of a carboxylic acid selected from the group consisting of phthalic acid, a tetrahydrophthalic acid, hexahydrophthalic acid and maleic acid, or of an alkyl or nitro-substituted compound of the carboxylic acid, and also provides an electrolytic c

REFERENCES:
patent: 3539881 (1970-11-01), Anderson
patent: 3812039 (1974-05-01), Niwa
patent: 3872358 (1975-03-01), Murakami et al.
patent: 4117531 (1978-09-01), Ross et al.
patent: 4377692 (1983-03-01), Barry et al.
patent: 4715976 (1987-12-01), Mori et al.
patent: 4734821 (1988-03-01), Morimoto et al.

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