Non-aqueous electrolytic solution for capacitor and...

Details Non-aqueous electrolytic solution for capacitor and... Non-aqueous electrolytic solution for capacitor and...

1998-09-11

2001-11-13

Koslow, C. Melissa (Department: 1755)

Compositions

Electrolytes for electrical devices

C361S502000, C361S503000, C429S330000, C429S331000

Reexamination Certificate

active

06315918

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a non-aqueous electrolytic solution for capacitors which contains primarily cyclic carbonic ester, specifically a non-aqueous electrolytic solution for electric double layer capacitors, more specifically a capacitor showing high energy density and excellent with-stand voltage and charging/discharging cycle properties, and especially a non-aqueous electrolytic solution that can provide electric double layer capacitors.
TECHNICAL BACKGROUND
Up to the present, capacitors, particularly electric double layer capacitors having a capacity intermediate between that of a battery and that of a capacitor, as a backup power supply for IC's and memories and a supplement or alternative to secondary batteries, have been used widely as a low-power direct-current power supply. In recent years, however, there have been new portable electronic devices coming into being one after another, such as VTR with a built-in camera, cellular phones and laptop computers. Amid this trend, there has been a growing demand that those electric double layer capacitors used as a backup power supply and a supplement or alternative to secondary batteries should have higher energy density.
These electric double layer capacitors, unlike batteries, do not convert a chemical change into electric energy. They utilize a large capacity of the electric double layer that occur between the electrodes and the electrolytic solution to put in and out an electric charge in the same manner as the charge and discharge of batteries. Such electric double layer capacitors are normally so constructed that they use a non-corrosive electrolytic solution that does not corrode the capacitor container or the collector made of aluminum, copper or the like and two electrodes formed from a material having a large surface area such as activated carbon and a binder such as fluororesins are so arranged that they face each other via a porous separator made of polyethylene or polypropylene.
As the electrolytic solution for such electric double layer capacitors, aqueous-solution-based electrolytic solution and organic-solvent-based electrolytic solution (non-aqueous electrolytic solution) are used. However, aqueous-solution-based electrolytic solution showing low potential window of electrochemical stability (approx. 1.2 V) are difficult to provide high-energy-density electric double layer capacitors.
By contrast, compared with aqueous-solution-based electrolytic solution, organic-solvent-based electrolytic solution (non-aqueous electrolytic solution) show high potential window of electrochemical stability and therefore make the formation of high-energy-density capacitors possible. Because of this, the electric double layer capacitors using non-aqueous electrolytic solution are rapidly beginning to come into use as a backup power supply for electronic equipment for non-military use.
As such non-aqueous electrolytic solution, a mixture of a non-aqueous solvent such as cyclic carbonic ester exhibiting a high dielectric constant and an electrolyte such as tetraethylammonium tetra fluoroborate, for example, is used.
However, such an electrolytic solution as mentioned above has had the problem of the inner electrical resistance of the A capacitor going up due to its low electric conductivity, making it difficult to obtain high-output capacitors. Furthermore, when future capacitors have high energy density, the aforementioned electrolytic solution might be insufficient in potential window of electrochemical stability. Because of this, it has been hoped that a non-aqueous electrolyte having better charging/discharging cycle properties will come into existence.
SUMMARY
The inventors of the present invention sought a solution to the problems of the conventional technology as described above. The present invention is intended to provide non-aqueous electrolytic solutions which release little gas, have excellent potential window of electrochemical stability and enable capacitors to show excellent charging/discharging cycle properties and safety performance, and capacitors containing such non-aqueous electrolytic solutions.
The non-aqueous electrolytic solution for capacitors of the present invention comprises an electrolytic solution containing at least one cyclic carbonic ester selected from compounds of the following (1), (2) and (3) and an electrolyte:
(1) A compound which is represented by Formula (I):
(wherein R
1
to R
4
, which may be the same or different, are hydrogen, the alkyl group, the unsaturated hydrocarbon group or the aryl group or a group represented by —CH
2
—O—A, wherein A stands for R
5
, CO—R
5
or —CO—O—R
5
[wherein R
5
is the alkyl group or the unsaturated hydrocarbon group]); said compound being such that:
(i) In Formula I, at least one of R
1
to R
4
is the aforementioned group represented by —CH
2
—O—A, with the remaining groups selected from among hydrogen, the alkyl group and the unsaturated hydrocarbon group.
(ii) In Formula I, at least one of R
1
to R
4
is the unsaturated hydrocarbon group, with the remaining groups selected from among hydrogen, the alkyl group, the aryl group and the unsaturated hydrocarbon group.
(iii) In Formula I, at least one of R
1
to R
4
is an aryl group and the remaining R
1
to R
4
are selected from among the alkyl group and the aryl group.
(2) A compound which is represented by Formula (II):
(wherein R
6
and R
7
, which may be the same or different, is hydrogen atom, the alkyl group or the unsaturated hydrocarbon group); and
(3) A compound which is represented by Formula (III):
(wherein R
8
and R
9
, which may be the same or different, are the alkyl group, the aryl group or the unsaturated hydrocarbon group).
The present invention also provides capacitors containing the electrolytic solution comprising the electrolyte solvent containing the cyclic carbonic ester of the present invention and an electrolyte.
The non-aqueous electrolytic solution for capacitors of the present invention releases a little gas and shows high potential window of electrochemical stability and excellent safety performance and charging/discharging cycle properties.
Especially, the use of the non-aqueous electrolytic solution for capacitors of the present invention in the formation of capacitors enables the obtaining of capacitors which generate high voltage, release a little gas and show excellent charging/discharging cycle properties and energy density. This effect manifests itself markedly especially when the electrolytic solution is used in electric double layer capacitors.


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abstract for JP 8-222,234.*
abstract for JP 6-52887.

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