NON-AQUEOUS ELECTROLYTE ELECTRIC DOUBLE-LAYER CAPACITOR,...

Details NON-AQUEOUS ELECTROLYTE ELECTRIC DOUBLE-LAYER CAPACITOR,... NON-AQUEOUS ELECTROLYTE ELECTRIC DOUBLE-LAYER CAPACITOR,...

2000-11-09

2002-09-17

Reichard, Dean A. (Department: 2831)

Electricity: electrical systems and devices

Electrolytic systems or devices

Liquid electrolytic capacitor

C361S508000, C361S528000, C361S503000, C361S521000, C429S328000, C429S329000, C029S025030

Reexamination Certificate

active

06452782

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a non-aqueous electrolyte electric double-layer capacitor used in various types of energy reserves such as backup power supplies, auxiliary power supplies and the like, and which has superior self-extinguishability or incombustibility, an additive used for the non-aqueous electrolyte electric double-layer capacitor and an deterioration inhibitor used for the non-aqueous electrolyte electric double-layer capacitor which can effectively suppress the deterioration of the non-aqueous electrolyte electric double-layer capacitor.
2. Description of the Related Art
A non-aqueous electrolyte electric double-layer capacitor is a capacitor which utilizes an electric double-layer formed between a polarized electrode and an electrolyte. The non-aqueous electrolyte electric double-layer capacitor was developed and commercialized in the 1970s, underwent a period akin to early infancy in the 1980s, and experienced a period of growth and development period in the 1990s.
The non-aqueous electrolyte electric double-layer capacitor is different from a battery, whose charge-and-discharge cycle is a cycle of oxidation reduction reaction accompanying movements of substances, in that the charge-and-discharge cycle is a cycle in which ions are electrically adsorbed from an electrolyte on an electrode surface. The non-aqueous electrolyte electric double-layer capacitor has the following advantages, compared with a battery. That is, the non-aqueous electrolyte electric double-layer capacitor has a superior instantaneous charge-and-discharge property. Even if the charge-and-discharge cycle is repeated, the instantaneous charge-and-discharge property hardly deteriorates. Further, since a charge-and-discharge overvoltage is not generated at a time of the charge-and-discharge, it suffices as a simple and inexpensive electric circuit. Moreover, the remaining capacity of the non-aqueous electrolyte electric double-layer capacitor is easily known. The non-aqueous electrolyte electric double-layer capacitor has durable temperature properties under temperature conditions within a wide range of −30 to 90° C., and is non-polluting. Thus, the non-aqueous electrolyte electric double-layer capacitor has attracted interest recently as a new energy reserve product which is harmless to the global environment.
The non-aqueous electrolyte electric double-layer capacitor is an energy reserve device which has positive and negative polarized electrodes and an electrolyte. On a contact interface between the polarized electrodes and the electrolyte, positive charges and negative charges are arranged so as to face with each other with an extremely short distance therebetween so as to form an electric double-layer. Since the electrolyte serves as an ion source for forming the electric double-layer, similar to the polarized electrodes, the electrolyte is an important substance which controls the basic properties of the energy reserve device.
An aqueous electrolyte, a non-aqueous electrolyte, a solid electrolyte and the like have been conventionally known as the electrolyte. Among them, in view of improving the energy density of a non-aqueous electrolyte electric double-layer capacitor, the non-aqueous electrolyte has especially attracted interest because a high operational voltage can be set. The practical application thereof is proceeding.
For example, non-aqueous electrolytes, prepared by dissolving a solute (supporting electrolyte) such as (C
2
H
5
)
4
P.BF
4
, (C
2
H
5
)
4
N.BF
4
and the like in an organic solvent having a high dielectric constant such as carbonates (ethylene carbonate, propylene carbonate and the like), &ggr;-butyrolactone and the like, have been practically used.
However, in the case of these non-aqueous electrolytes, thre has been the problem that, since the flash points of solvents contained therein are low, if the non-aqueous electrolyte electric double-layer capacitor ignites by generated heat, the non-aqueous electrolyte also ignites. Flames spread on the surface of the non-aqueous electrolyte, and it is highly dangerous. There has also been the problem that vaporization and decomposition of the non-aqueous electrolyte due to heat or the like can generate gas which causes the non-aqueous electrolyte electric double-layer capacitor to burst or ignite, thereby the non-aqueous electrolyte also ignites and flames spread on the surface of the non-aqueous electrolyte. It is therefore highly dangerous.
Recently, accompanying the practical use of the non-aqueous electrolyte electric double-layer capacitor, expectations have come to be placed on the application thereof to electric cars, hybrid cars and the like. The demand for the safety of the non-aqueous electrolyte electric double-layer capacitor continues to escalate each day. Further, since the non-aqueous electrolyte electric double-layer capacitor has high performance but is generally easy to deteriorate, the development of technology in which the deterioration of the non-aqueous electrolyte electric double-layer capacitor can be avoided and characteristics thereof can be highly maintained for a long time is in strong demand.
In the midst of such circumstances, development has been anticipated of a non-aqueous electrolyte electric double-layer capacitor which has inherently high safety regardless of safety measures such as providing of an accessory component such as a safety valve or the like, which has self-extinguishability, in which it becomes difficult for flames to spread even if a non-aqueous electrolyte contained therein ignites, or flame-resistance in which it becomes difficult for the non-aqueous electrolyte to ignite, which has superior resistance to deterioration, superior properties at low temperatures, long term stability, and can be easily manufactured, and of an additive therefor.
SUMMARY OF THE INVENTION
The present invention has been devised in order to satisfy such demands, to resolve conventional problems and to accomplish the following objects.
A first object of the present invention is to provide a non-aqueous electrolyte electric double-layer capacitor which has superior resistance to deterioration in which the surface resistance of the non-aqueous electrolyte is low, and which has superior properties at low temperatures, while maintaining electrical characteristics such as sufficient electric conductivity and the like.
A second object of the present invention is to provide a non-aqueous electrolyte electric double-layer capacitor which has superior self-extinguishability or flame-resistance, in which the surface resistance of the non-aqueous electrolyte is low, and which has superior properties at low temperatures, while maintaining electrical characteristics such as sufficient electric conductivity and the like.
A third object of the present invention is to provide an deterioration inhibitor for a non-aqueous electrolyte electric double-layer capacitor which, by being added into the non-aqueous electrolyte in the non-aqueous electrolyte electric double-layer capacitor, can prevent deterioration of the non-aqueous electrolyte, can lower the surface resistance of the non-aqueous electrolyte, which can give superior properties at low temperatures, while maintaining electrical characteristics such as sufficient electric conductivity and the like.
A fourth object of the present invention is to provide an additive for a non-aqueous electrolyte electric double-layer capacitor which, by being added into the non-aqueous electrolyte in the non-aqueous electrolyte electric double-layer capacitor, can give self-extinguishability or incombustibility to the non-aqueous electrolyte, which can lower the surface resistance of the non-aqueous electrolyte, and which can give superior properties at low temperatures, while maintaining electrical characteristics such as sufficient electric conductivity and the like.
A first aspect of the non-aqueous electrolyte electric double-layer capacitor of the present invention in order to accomplish the first object ha

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