Electrolytic solution

#The present invention relates to an electrolytic solution comprising a chain carbonate having, at least at one end thereof, a fluorine-containing ether group having CF3 at its end and an electrolyte salt.

#Carbonates such as ethylene carbonate, propylene carbonate and dimethyl carbonate are used as a solvent for an electrolyte salt of lithium secondary battery, solar cell, radical battery and capacitor. However since a flash point is low and combustibility is high, there is a danger of firing and explosion attributable to over-charging and over-heating, and in addition, since viscosity is high and conductivity at low temperatures is low, there is a problem that an output is decreased.

#In order to solve those problems, it is proposed to use a fluorine-containing chain carbonate obtained by fluorinating a chain carbonate. For example, there are proposed carbonates in which an end of a fluorine-containing alkyl group is perfluoro, such as a carbonate having a fluorine-containing alkyl group at one end thereof and a hydrocarbon alkyl group at another end (JP6-219992A), a dicarbonate having an ethylene in its center and CF3(CF2)(CH2)— at both ends thereof (JP10-149840A) and a carbonate having hexafluoroisopropyl groups at both ends thereof (JP2001-256983A), and in addition, a carbonate having a fluorine-containing ether group at one end thereof and a hydrocarbon alkyl group at another end thereof (JP2000-327634A).

#The electrolytic solution of the present invention comprises the specific chain carbonate (I) which is a solvent for dissolving an electrolyte salt and has a CF3-terminated fluorine-containing ether group and the electrolyte salt (II).

#The chain carbonate (I) having a CF3-terminated fluorine-containing ether group which is used in the present invention is represented by the formula (I):

#wherein Rf1 is a fluorine-containing ether group (Ia) having CF3 at its end, preferably a fluorine-containing ether group having 2 to 16 carbon atoms: Rf2 is a fluorine-containing ether group, preferably a fluorine-containing ether group having 2 to 16 carbon atoms and containing CF3 or CH3 at its end or a fluorine-containing alkyl group, preferably a fluorine-containing alkyl group having 2 to 16 carbon atoms and containing CF3 or CH3 at its end.