NOVELTY - An electrolyte solution consists of supporting electrolyte salt (0.1-2 mol/l) and solvent composition comprising cyclic carbonic acid ester solvent(s) (0-90 vol.%) and fluorine-containing solvent(s) (0-80 vol.%) having boiling point of 80degreesC.    USE - For lithium secondary battery (claimed), electrochemical energy device and cell double layer capacitor.    ADVANTAGE - The electrolyte solution provides batteries having excellent charging-and-discharging characteristics and excellent low temperature charging-and-discharging performance. Favorable battery capacity is maintained over a long period of time.    DETAILED DESCRIPTION - An electrolyte solution consists of supporting electrolyte salt (0.1-2 mol/l) and solvent composition comprising cyclic carbonic acid ester solvent(s) (0-90 vol.%) and fluorine-containing solvent(s) (0-80 vol.%) having boiling point of 80degreesC. The fluorine-containing solvent is chosen from compounds of formulae (i-iii): R1-O-Rf1, R2-O-(Rf2-O)p(Rf3-O)qR3, and A-(O-Rf4)m.    R1 = optionally branched or cyclic 1-12C alkyl, aryl or alkenyl group;    Rf1 = partially fluorinated optionally branched or cyclic 5-12C alkyl, aryl or alkenyl optionally containing ether-bound oxygen atom(s);    R2,R3 = linear or branched, non- or partially fluorinated 1-12C alkyl group;    Rf2,Rf3 = optionally branched or cyclic 1-10C fluorinated alkylene group;    p,q = 0 or 1-10, p,q are not 0 at the same time;    Rf4 = partially fluorinated optionally branched or cyclic 2-9C alkyl, aryl or alkenyl group optionally containing ether-bound oxygen atom(s) and/or halogen atom other than fluorine;    A = 1-8C di- to tetravalent optionally branched or cyclic hydrocarbon optionally containing ether-bound oxygen atom(s);and    m = 2-4.    When m is 2, Rf4 is perfluorinated and/or A is non-linear. Rf1 contains oxygen atom(s) and two hydrogen atoms. When the solvent composition comprises only a fluorine-containing solvent of formula (i), the solvent composition does not contain difluoroethylene carbonate.    An INDEPENDENT CLAIM is included for lithium secondary battery, which consists of anode, cathode and the electrolyte solution.