Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Include electrolyte chemically specified and method
Reexamination Certificate
2000-08-24
2002-12-17
Weiner, Laura (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Include electrolyte chemically specified and method
C429S316000, C429S322000, C429S341000, C429S231950, C429S224000
Reexamination Certificate
active
06495293
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a non-aqueous electrolyte, a solid electrolyte, lithium secondary batteries, and electrochemical capacitors; and, more particularly, the invention relates to an improvement in the diffusivity of electrolyte and a solid electrolyte, to the improvement in load performance of batteries and polymer secondary batteries at a low temperature, and to improvement in the charge-discharge performance of electrochemical capacitors.
A non-aqueous electrolyte using an organic solvent has a high anti-oxidant performance in comparison with an aqueous electrolyte; and, a non-aqueous electrolyte is widely used for lithium primary batteries and lithium secondary batteries, which are driven with a voltage higher than the oxidation voltage of water, as well as for electrochemical capacitors exceeding the 2V class, and the like. Generally, for a non-aqueous electrolyte, organic solvents of a cyclic and linear chain carbonate ester, such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and the like; a cyclic and linear chain ether, such as dimethoxy methane, 1,2-dimethoxy ethane, digryme, trigryme, 1,3-dioxolane, tetrahydrofuran, 2-methyl tetrahydrofuran, and the like; &ggr;-butylolactom, sulfolane, methyl propionate, ethyl propionate, and others are used. However, these solvents have a larger molecular weight in comparison with a water molecule, and so disadvantages result due to solubility and dissociation, because the number of molecules of the solvent is small in an equivalent salt concentration. Furthermore, the diffusivity of ions is decreased, because the volume of solvation to ions becomes larger than water, and a decreasing capacity performance of batteries and capacitors is generated at a low temperature or high rate load with the non-aqueous electrolyte.
A solid electrolyte, which is formed by impregnating a non-aqueous electrolyte into a foamed polymer material, such as polyvinylidene fluoride (hereinafter, called as PVDF) and the like, and a gel group solid polymer electrolyte, which uses a gel formed by the steps of melting a polymer such as polyethylene oxide (hereinafter, called as PEO) with a non-aqueous electrolyte at a high temperature and cooling the mixture to room temperature as an electrolyte, makes it possible to make the outer container of the batteries thin and light weight, because the electrolyte creates no problems concerning liquid. leakage in the batteries, nor the necessity to use a strong battery can. Therefore, currently, polymer batteries using these electrolytes have been developed and have come to be mounted in portable telephones and the like. These polymer electrolytes have an even lower diffusivity of ions in comparison with liquid non-aqueous electrolytes, and their operation performance at a low temperature and high rate load is further decreased.
A non-aqueous electrolyte has a low electric conductivity in comparison with an aqueous electrolyte and is inferior to the aqueous electrolyte in low temperature characteristics and load characteristics. In order to solve such problems, U.S. Pat. No. 5,795,677 discloses a non-aqueous electrolyte which includes a fluorinated ether having a structure in which a fluorinated alkyl chain and ether oxygen are connected via a —CH
2
— structure. In accordance with the above prior art, the low temperature characteristics and load characteristics are certainly improved by mixing the fluorinated solvent.
However, in the case of the above prior art, wherein the fluorinated alkyl chain and ether oxygen are connected via a —CH
2
— structure, the decrease in the electron density on the ether oxygen is small, and an interaction between the fluorinated ether and lithium ions is produced. Therefore, the fluorinated ether is solvated with lithium ions, and an advantage in which the improvement in diffusivity of lithium ions produced by mixing the fluorinated solvent can not be achieved sufficiently.
SUMMARY OF THE INVENTION
One of the objects of the present invention is to provide a non-aqueous electrolyte having a high diffusivity; a polymer electrolyte having a high diffusivity; and non-aqueous electrolyte group batteries, electrochemical capacitors, and polymer secondary batteries, the performance at a low temperature of which is improved by using the above electrolyte.
The above object can be achieved by mixing a fluorinated solvent indicated by a chemical formula 1 into the non-aqueous electrolyte. If lithium salt is used as a supporting electrolyte of the non-aqueous electrolyte, the electrolyte can be used as the electrolyte for lithium primary battery and a lithium secondary battery, and the diffusivity of the lithium ions can be improved. Furthermore, the performance of these batteries at a low temperature can be improved by using such an electrolyte. If quaternary onium salt is used as a supporting electrolyte, the electrolyte can be used as the electrolyte for electrochemical capacitors, and the performance of these capacitors at a low temperature can be improved by using the electrolyte. Furthermore, the diffusivity of lithium ions in a polymer electrolyte can be improved by mixing the fluorinated solvent expressed by the chemical formula 1 into a polymer electrolyte composed of a mixture of a polymer compound and a non-aqueous electrolyte, and the performance of the polymer secondary batteries at a low temperature can be improved by using the electrolyte.
The fluorinated solvent to be mixed into an electrolyte is ethyl ether of fluorinated alkyl carboxylic acid, the terminal end of the fluorinated alkyl of which is a difluoromethyl group, expressed by the following chemical formula 5, which has a structure in which the fluorinated alkyl group is directly combined with functional group:
(wherein, s indicates any one of integers of 0, 3, 5, 7, and 9), or
fluorinated alkyl iodide, the terminal end of the fluorinated alkyl of which is a difluoromethyl group, expressed by the following chemical formula 6:
(wherein, t indicates any one of integers of 1, 3, and 5), or
fluorinated solvent, in which both terminal ends of its molecule are isoheptafluoropropyl groups, expressed by the following chemical formula 7:
(wherein, u indicates an integer of 4 or 8), or
fluorinated alkyl acrylate compound, the terminal end of the fluorinated alkyl of which is a difluoromethyl group, expressed by the following chemical formula 8:
(wherein, v indicates any one of integers of 4, 6, 8, and 10), or
fluorinated alkyl methacrylate compound, the terminal end of the fluorinated alkyl of which is a difluoromethyl group, expressed by the following chemical formula 9:
(wherein, w indicates any one of integers of 4, 6, 8, and 10), or
a compound expressed by the following chemical formula 10:
(wherein, n indicates an integer in the range of 2-6, and R
4
indicates any one of methyl group, ethyl group, and propyl group), for instance, any one of ether of H(CF
2
)
2
OCH
3
, H(CF
2
)
2
OCH
2
CH
3
, H(CF
2
)
2
OCH
2
CF
3
, and the like, or ether of CF
3
CHFCF
2
OCH
3
, CF
3
CHFCF
2
OCH
2
CH
3
, or iso-perfluoroalkyl alkyl ether expressed by the chemical formula 4, that is, 2-trifluoromethyl hexafluoropropyl methyl ether, 2-trifluoromethyl hexafluoropropyl ethyl ether, 2-trifluoromethyl hexafluoropropyl propyl ether, 3-trifluoro octafluorobutyl methyl ether, 3-trifluoro octafluorobutyl ethyl ether, 3-trifluoro octafluorobutyl propyl ether, 4-trifluorodecafluoropenthyl methyl ether, 4-trifluorodecafluoropenthyl ethyl ether, 4-trifluorodecafluoropenthyl propyl ether, 5-trifluorododecafluorohexyl methyl ether, 5-trifluorododecafluorohexyl ethyl ether, 5-trifluorododecafluorohexyl propyl ether, 6-trifluorotetradecafluoroheptyl methyl ether, 6-trifluorotetradecafluoroheptyl ethyl ether, 6-trifluorotetradecafluoroheptyl propyl ether, 7-trifluorohexadecafluorooctyl methyl ether, 7-trifluorohexadecafluorooctyl ethyl ether, and 7-trifluorohexadecafluorohexyl octyl ether can be used. Furthermore, a mixture of any one of the a
Arai Juichi
Katayama Hideaki
Kobayashi Mitsuru
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Weiner Laura
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