TECHNOLOGY FOCUS - ELECTRONICS - Preferred Property: The thickness variation rate of the electrochemical device after leaving at 90 degrees C for 4 hour is 10% or less.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Compound: The amide compound is N-methoxyethyl methylcarbamate, N-methoxyethyl-N-methyl methylcarbamate, N-methoxymethyl-N-methyl methylcarbamate, N,N-dimethyl methoxyethyl carbamate, N-methyl methoxymethyl methoxyethyl carbamate, N-methyl-N-methoxyethyl methoxyethyl carbamate, N-methyl-N-methoxyethyl methoxymethyl carbamate, N-methoxyethyl caprolactam, N-methoxyethyl oxazolidone, N-methoxyethyl-N-methylphenylthio carbamate or N-methoxyethyl-N-methyl piperidine carbamate.The lithium salt contains anion chosen from fluoride, chloride, bromide, iodide, NO3-, N(CN)2-, tetrafluoroborate, perchlorate, hexafluorophosphate, (CF3)2PF4-, (CF3)3PF3-, (CF3)4PF2-, (CF3)5PF5-, (CF3)6P-, CF3SO3-, CF3CF2SO3-, (CF3SO2)2N-, (FSO2)2N-, CF3CF2(CF3)CF2CO- (sic), (CF3SO2)2CH-, (SF5)3C-, (CF3SO2)3C-, CF3(CF2)7SO3-, CF3CO2-, CH3CO2-, SCN- and (CF3CF2SO2)2N-.The molar ratio of the lithium salt and amide compound is 1-1:1.The deoxidation electric potential of the eutectic mixture of lithium salt and the amide compound is 0.4-0.55V. The ionizable deoxidation electric potential of the eutectic mixture and amide compound is 0.7-0.9V.The carbonate is chain shaped carbonate and/or cyclic carbonate, preferably polypropylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), butylene carbonate, methylpropyl carbonate, ethylpropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methylpyrrolidone (NMP), ethyl methyl carbonate (EMC) and/or gamma -butyrolactone. The content of the carbonate compound with respect to 100 weight parts of the eutectic mixture is 5-200 weight parts. The electrolyte has viscosity of 50 cP or less, preferably 4-30 cP or less and ion conductivity of 5-10 mS/cm.    TECHNOLOGY FOCUS - POLYMERS - Preferred Component: The electrolyte is polymer electrolyte of gel-like obtained by polymerizing precursor solution containing carbonate type compound, the eutectic mixture, amide compound and monomer chosen from acrylonitrile, methylmethacrylate, methyl acrylate, methylstyrene, vinyl ester group, polyvinyl chloride, vinylidene chloride, acrylamide, tetrafluoroethylene, vinyl acetate, vinyl chloride, methylvinyl ketone, ethylene, styrene and/or para cyanostyrene. Alternately, the electrolyte contains polymer dipped in mixture of carbonate type compound and eutectic mixture. The polymer is polymethyl methacrylate, polyvinylidene difluoride, polyvinylchloride, polyethylene oxide and/or polyhydroxyethylmethacrylate.