Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Include electrolyte chemically specified and method
Reexamination Certificate
1998-06-22
2001-05-22
Chaney, Carol (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Include electrolyte chemically specified and method
C429S307000
Reexamination Certificate
active
06235431
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a nonaqueous electrolytic solution for a battery and a nonaqueous electrolytic solution battery. More particularly, the present invention relates to a secondary lithium battery comprising a nonaqueous electrolytic solution containing a predetermined halogen compound as a supporting electrolyte. Even more particularly, the present invention relates to a nonaqueous electrolytic solution for a battery which is arranged to prevent the production of hydrogen halide due to inevitable inclusion of a small amount of water content and a nonaqueous electrolytic solution battery comprising such a nonaqueous electrolytic solution.
BACKGROUND OF THE INVENTION
A nonaqueous electrolytic solution battery comprising lithium or a compound thereof as an active electrode material and therefore an organic solvent dissolving a supporting electrolyte therein as an electrolytic solution has been noted for its usefulness as a primary battery as a small-sized power supply for electronic parts or a secondary battery or lithium ion battery for electric automobiles.
Referring further to such a nonaqueous electrolytic solution battery, as the supporting electrolyte there is often used, e.g., halide such as LiPF
6
. However, if the electrolytic solution, which is supposed to be nonaqueous, inevitably contains some water content or has adsorbed water from other battery materials, the following reaction (1) takes place to produce a hydrogen halide such as hydrogen fluoride HF.
LiPF
6
+H
2
O→2HF+LiF+POF
3
(1)
Hydrogen fluoride deteriorates materials constituting the battery, causing further deterioration of battery properties. It is also known that the foregoing reaction (1) is accelerated at high temperatures. Therefore, these problems become remarkable when the nonaqueous electrolytic solution battery is used as a secondary battery for electric automobiles which must operate stably at a temperature of from −30° C. to 60° C. Thus, it is said that a nonaqueous electrolytic solution battery comprising LiPF
6
as a supporting electrolyte can hardly be applied to such a use.
In order to overcome these difficulties, some proposals have been made. For example, JP-A-4-284372 (The term “JP-A” as used herein means an “unexamined published Japanese patent application”), which concerns an improvement in a nonaqueous electrolytic solution secondary battery, proposes that an oxide selected from the group consisting of Al
2
O
3
, MgO and BaO, if incorporated in a nonaqueous electrolytic solution containing LiPF
6
as a supporting electrolyte, adsorbs hydrogen fluoride produced in the electrolytic solution so that hydrogen fluoride is removed from the reaction system.
JP-A-7-122297, which concerns an improvement in a nonaqueous electrolytic solution battery, proposes that an acid anhydride (e.g., acetic anhydride), if incorporated in a nonaqueous electrolytic solution containing LiPF
6
as a supporting electrolyte, previously catches water in the electrolytic solution to inhibit the foregoing reaction (1).
However, the above cited JP-A-4-284372 has some disadvantages. In accordance with duplicate experiments of the foregoing patent made by the present inventors, on the addition of some oxides to the extent within an actually acceptable amount for a battery, the removal of hydrogen fluoride proceeds too slowly to keep pace with the production of hydrogen fluoride. Accordingly, the foregoing proposal cannot effectively inhibit the deterioration of battery due to hydrogen fluoride.
On the other hand, the above cited JP-A-7-122297 exerts a high dehydration effect by an acid anhydride. As a result, however, an acid derived from the acid anhydride is produced. In other words, the foregoing proposal merely contemplates the substitution of other acids for hydrogen halide. Acetic acid or the like is relatively weaker than hydrogen halide but still deteriorates an electrolytic solution and battery can. Accordingly, the foregoing proposal provides no essential solution to the problems of the prior art.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an effective prevention of hydrogen halide formation in a nonaqueous electrolytic solution for a battery containing a supporting electrolyte which can react with water to produce a hydrogen halide, and a nonaqueous electrolytic solution battery using the same.
It is another object of the present invention to prevent the occurrence of the foregoing secondary problems of the prior art.
It is further object of the present invention to provide a nonaqueous electrolyte battery having a longer life and an excellent high-temperature stability.
These and other objects of the present invention will become more apparent from the following detailed description and examples.
The inventors made studies of dehydrating agents for eliminating water content that causes the production of a hydrogen halide. As a result, the inventors found that specific organic compounds, particularly a group of specific organosilicon compounds and a group of specific acetal compounds are useful for the solution to the accomplishment of the foregoing objects. Thus, the present invention has been worked out. Embodiments of the present invention will be given below.
(1) A nonaqueous electrolytic solution for a battery, comprising an organic solvent which could contain water, a supporting electrolyte which can react with water to produce a hydrogen halide, and an organosilicon compound having an Si-N bond, which reacts with said water and said hydrogen halide to decompose them.
(2) A nonaqueous electrolytic solution for a battery, comprising an organic solvent which could contain water, a supporting electrolyte which can react with water to produce a hydrogen halide, and an acetal compound which reacts with said water to decompose it.
(3) A nonaqueous electrolytic solution battery, comprising an active electrode material of lithium or a compound thereof and a nonaqueous electrolytic solution according to the foregoing embodiment (1) or (2).
In accordance with the foregoing embodiment (1), even if a small amount of water is incorporated into the nonaqueous electrolytic solution or a free hydrogen halide is produced in the nonaqueous electrolytic solution by the reaction of the water with the supporting electrolyte, the water and the hydrogen halide react with the organosilicon compound so that they are decomposed. This effect is exerted also in the embodiment (3).
This organosilicon compound reacts with water or a hydrogen halide very rapidly. Thus, the present invention is not liable to disadvantages due to the lower rate of reaction as in the above cited JP-A-4-284372. Further, the present invention is not liable to the disadvantage that other harmful substances are secondarily produced as in the above cited JP-A-7-122297.
In accordance with the foregoing embodiments (2) and (3), even if a small amount of water is incorporated into the nonaqueous electrolytic solution, the water reacts with the acetal compound so that it is decomposed.
This acetal compound reacts with water very rapidly. Thus, the present invention is not liable to disadvantages due to the lower rate of reaction as in the above cited JP-A-4-284372. Further, in the present invention, the acetal compound and water react with each other as represented by the formula (VII) given later to give a product which is harmless to the battery properties. Thus, the present invention is not liable to the disadvantage that other harmful substances are secondarily produced as in the above cited JP-A-7-122297.
Thus, despite of the use of a supporting electrolyte which can react with water to produce an acid, the nonaqueous electrolytic solution for a battery of the present invention is not liable to deterioration of the materials constituting the battery or the battery properties even if the nonaqueous electrolytic solution has water incorporated therein.
REFERENCES:
patent: 3511716 (1970-05-01), Gabano et al.
patent: 5631106 (1997-05-01), Dah
Shiga Tohru
Takechi Kensuke
Chaney Carol
Kabushiki Kaisha Toyota Chuo Kenkyusho
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Tsang Susy
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