Polycarbonate electrolyte, the preparation thereof and...

Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Include electrolyte chemically specified and method

Reexamination Certificate

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C429S188000, C429S303000, C429S306000, C429S307000, C429S310000, C429S320000, C429S336000, C429S338000, C429S347000

Reexamination Certificate

active

06300016

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a polycarbonate electrolyte. More particularly, it relates to a polycarbonate electrolyte composition, its preparation and its application in lithium batteries.
DESCRIPTION OF THE RELATED ARTS
Because lithium batteries have excellent performance in both energy density and battery life, they have been widely applied in recent years. However, with the miniaturization of semi-conductor devices and the increased performance of portable electronic products in the market, there has been a demand for lighter and thinner lithium batteries.
Traditional lithium batteries use liquid organic electrolyte, and thus must be enclosed in a metal can. Due to thickness requirements in the production of the metal can, a lithium battery having liquid organic electrolyte is limited in terms of thickness. Therefore, it cannot meet the current demands for a lighter and thinner battery.
Thus, in recent years, a polymer lithium battery in which the liquid organic electrolyte is replaced by polymer electrolyte has been formatively developed. Because it is not enclosed in metal can, the thickness limitations are decreased. However, conventional polymer does not have the same conductivity as liquid organic electrolyte. Thus, the development of a polymer electrolyte which has a conductivity close to that of liquid organic electrolyte (about 10
−3
&OHgr;
−1
cm
−1
) is crucial to the success of a polymer lithium battery.
Recently, many polymer electrolytes have been disclosed one after the other, such as polyethylene oxides, polyacrylates, polyacrylnitrides and polyvinylidene fluoride/hexafluoropropylenes. Of these, the polymer electrolyte of polyvinylidene fluoride/hexafluoropropylenes has attracted the greatest attention. As proposed by Bellcore in 1994, a co-polymer polyvinylidene fluoride/hexafluoropropylene polymer is mixed with a plasticizer to form a polymer membrane. Then a solvent is used to extract the plasticizer to obtain a porous polymer membrane. Like a sponge, the porous polymer membrane can be impregnated with or adsorb electrolytic solution. The electrolytic solution permeates into the porous polymer membrane, thereby preserving the electrolytic solution in the polymer membrane without spilling. Furthermore, polyvinylidene fluoride/hexafluoropropylene has the advantages of mechanical stability, flame-resistance and electrochemical stability.
However, polyvinylidene fluoride/hexafluoropropylene is a fluoride compound and its production generates heavily toxic hydrogen fluoride, which is a strong irritant and corrosive to humans. This raises the cost due to safety requirements at the manufacturing facility. Therefore, the development of a new polymer electrolyte which is inexpensive, safe to produce, and environmentally friendly is a key developing point in the field of lithium batteries.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a polymer electrolyte which has high ionic conductivity and excellent electrochemical stability, and is inexpensive, safe to produce and environmentally friendly.
The above object of the invention is attained by using a polycarbonate electrolyte. The polycarbonate electrolyte of the invention is a sponge-like, porous membrane matrix impregnated with lithium salt-containing electrolyte solution. Thus, the polymer electrolyte of the present invention has the advantage that the electrolytic solution can be preserved without spilling. The polycarbonates electrolyte has an ionic conductivity up to 3×10
−3
&OHgr;
−1
cm
−1
and excellent electrochemical stability. Moreover, since the polycarbonate polymer is not a fluoride compound, its synthesis does not generate heavily toxic hydrogen fluoride, and thus is cheaper to produce, safer, and more environmentally friendly.


REFERENCES:
patent: 11060870 (1999-03-01), None

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