Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Include electrolyte chemically specified and method
Patent
1992-02-10
1995-08-01
Kalafut, Stephen
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Include electrolyte chemically specified and method
429197, 429198, H01M 1040
Patent
active
054379440
DESCRIPTION:
BRIEF SUMMARY
This application is a national phase application of PCT application no. PCT/JP91/00787, filed in Japan on Jun. 12, 1991, published as WO 91/20104.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an organic electrolytic solution cell, and more particularly, it relates to an improvement of the organic electrolytic solution of such cell.
2. Description of the Related Art
The organic electrolytic solution cell, such as a lithium-manganese-dioxide cell which comprises a lithium negative electrode, a manganese dioxide positive electrode and an organic electrolytic solution, has increasingly come into wide use, because of its high energy density, light weight and long-life.
As an electrolyte for the organic electrolytic solution cell, LiClO.sub.4 is commonly used. (See, for example, T. Iwamaru, O. Kajii, Practical Lithium Batteries, p53 (1988).
A cylindrical lithium-manganese dioxide cell has also increasingly come into wide use as a battery of a camera. Combinations of the electrolytic solution such as a cyclic ether and the electrolyte have been studied in order to provide excellent characteristics even at a low temperature.
Consideration as to safety is important for a big size cell such as the cylindrical lithium-manganese dioxide cell, because it is dangerous if a fire or a detonation occurs by any chance.
Generally, this type of the cell is provided with the PTC device a resistance of which increases to decrease the intensity of an electric current when a temperature of the cell rises abnormally by an electric current or heat or a safety valve device, which exhausts the inner gas in the cell through a vent hole to prevent explosion of the cell under high pressure, when an inner pressure of the cell is increased abnormally by generation of gas in the cell. However, the cell may be fired after continuation of the overdischarge under a large electric current without the PTC device.
For example, the cylindrical lithium-manganese dioxide cell comprising LiClO.sub.4 as the electrolyte, as shown in FIG. 1, which has an outer diameter of 15 mm and a height of 40 mm, abnormally generates heat when it is overdischarged at 4 A and discharged at a constant voltage of -3 V after reaching -3 V, and sometime causes the fire or the detonation.
To improve the thermal stability of the cell, it is proposed to use LiCF.sub.3 SO.sub.3 as an electrolyte. Though the cell using LiCF.sub.3 SO.sub.3 is stable under the normal condition, it generates abnormal heat when the discharge electric current exceeds 15 A.
Therefore the use of LiCF.sub.3 SO.sub.3 which effects to the safety only in the overdischarge is still insufficient.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an organic electrolytic solution cell which does not generate an abnormal heat during the overdischarge to maintain cell safety.
To achieve the above object, abnormal heat generation of the cell during overdischarge is prevented by using an organic metal salt in which a fluoroalkyl group having at least 4 carbon atoms and an anionic group are covalently bonded; and to the anionic group, an alkali metal ion or an alkaline earth metal ion is ionically bonded.
Herein, the anionic group is a substituent group such as --SO.sub.3 -- and --CO.sub.2 --, which is able to bond with an alkali metal ion or the alkaline earth metal ion.
The reason why the abnormal heat generation of the cell during the overdischarge is prevented by using the above electrolyte may be as follows.
When a large electric current flows in the cell and a temperature of the cell increases rapidly and reaches around the melting point of the separator, the separator is clogged and the current will not flow normally.
When the electric current is extremely large and the separator is rapidly clogged, the clogging is irregularly formed. Then, dendritic growth of the alkali metal, such as lithium, appears in the irregularly clogged area when the cell voltage is reversed during the overdischarge so that a short circuit is formed. In that
REFERENCES:
patent: 4074028 (1978-02-01), Will
patent: 5128222 (1992-07-01), Yoshizawa et al.
Dey, J. Electrochemical Soc.: Electrochemical Science "Electrochemical Studies on the Effect of Water in Nonaqueous Electrolytes" p. 823; Aug. 1967.
Kawakami Akira
Kita Fusaji
Hitachi Maxell Ltd.
Kalafut Stephen
LandOfFree
Organic electrolytic solution cell does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Organic electrolytic solution cell, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Organic electrolytic solution cell will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-733180