TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The lithium salt is lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluroantimonate, lithium hexafluoroarsenate, lithium bis-pentafluoroethanesulfonimide, lithium bis(trifluoromethanesulfonimide), lithium bis-pentafluoroethanesulfonate, lithium trifluoromethanesulfonate, lithium nonafluorobutanesulfonate, lithium benzenesulfonate, lithium thiocyanate, lithium aluminate, lithium chloroaluminate, fluorinated lithium salt of formula (LiN(CxF2x+1SO2)(CyF2y+1SO2)), lithium chloride, lithium iodide or lithium bisoxalatoborate. The concentration of lithium salt in the electrolyte is 0.1-2 M.x, y = natural numbers.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Composition: The electrolyte further comprises additive including oxalato borate compound, fluoro-carbonate compound, vinylidene carbonate compound and/or sulfinyl group-containing compound. Preferred Components: (I) is 3-(3-(2-cyanoethoxy)-2,2-bis((2-cyanoethoxy)methyl)propoxy)propanenitrile, diethyl bis(2-cyanoethyl)malonate, 4,4-dicyano-heptanedinitrile or 3-(3-(2-Cyano-ethoxy)-2-(2-cyano-ethoxymethyl)-propoxy)-propionitrile. The content of (I) in the electrolyte is 1-20 wt.%. The additive comprises lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, fluoro-ethylene carbonate, vinylene carbonate, vinyl ethylene carbonate, divinyl sulfone, ethylene sulfite, propylene sulfite, diallyl sulfonate, ethane sultone, propane sultone, butane sultone, ethene sultone, butene sultone and/or propene sultone. The content of additive in the electrolyte is 0.1-5 wt.%. The non-aqueous organic solvent is cyclic carbonate solvent and/or linear carbonate solvent. The cyclic carbonate comprises ethylene carbonate, polypropylene carbonate, butylene carbonate, vinylene carbonate, vinylethylene carbonate and/or fluorinated ethylene carbonate. The linear carbonate is dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methylpropyl carbonate, methylisopropyl carbonate and/or ethylpropyl carbonate. The non-aqueous organic solvent comprises linear carbonate solvent and cyclic carbonate solvent in a volume ratio of 1:1-9:1. EXAMPLE - 1 M lithium hexafluorophosphate solution (prepared by dissolving lithium hexafluorophosphate in 3:7 vol./vol. ethylene carbonate-ethyl methyl carbonate mixed solvent) and 10% 3-(3-(2-cyanoethoxy)-2,2-bis-(2-cyanoethoxymethyl)propoxy)propionitrile were mixed to obtain the electrolyte.