TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Electrolyte: The electrolyte additionally includes at least one of 1,3-propene sultone and vinylethylene carbonate. Preferred Components: The second additive is tris(trialkylsilyl)phosphate having 1-3C alkyl moiety (preferably tris(trimethylsilyl)phosphate); and included in an amount of 0.1-5 wt.%. The first additive is included in an amount of 0.1-5 wt.%, preferably lithium difluoro(oxalate) borate is included in an amount of 0.5-5 wt.%. Weight ratio of the first and second additives is 1:0.5 to 1:10 (preferably 1:0.5 to 1:4). The ester-based solvent is at least one of an alkyl acetate, an alkyl propionate or cyclic ester (preferably at least one of methyl propionate and ethyl propionate). The non-aqueous organic solvent further includes at least one of carbonate-based, ether-based, ketone-based, alcohol-based, and aprotic solvent along with the ester-based solvent (preferably carbonate-based solvent, especially at least one of cyclic carbonate and linear carbonate). EXAMPLE - A LiPF6 solution (1.15 M) was prepared by adding LiPF6 to mixed solvent prepared by mixing ethylene carbonate and ethyl propionate in weight ratio of 2:8. Then, lithium difluoro(oxalate) borate (0.5 wt.%) and tris(trimethylsilyl)phosphate (2 wt.%) were added to form non-aqueous electrolyte. Lithium nickel cobalt manganese oxide as a positive active material, polyvinylidene fluoride as a binder, and carbon as conductive material were mixed in a weight ratio of 92:4:4, and N-methyl-2-pyrrolidone was added to form positive slurry. The positive slurry was coated on 20 mu m-thick aluminum foil as a current collector, dried in 120 degrees C vacuum oven, and compressed to fabricate positive electrode. Natural graphite as negative active material and styrene-butadiene rubber as binder were mixed in weight ratio of 92:8. N-Methyl-2-pyrrolidinone was added to the mixture. The resulting mixture was dispersed, preparing negative electrode slurry. The negative electrode slurry was coated on 15 mu m-thick copper film as current collector, dried in 120 degrees C vacuum oven, and compressed, fabricating negative electrode. Then, 25 mu m-thick polyethylene porous film as a separator was disposed between the positive and negative electrode to form an electrode assembly. The electrode assembly was spiral-wound and compressed. The resulting product was put in a cylindrical can. The non-aqueous electrolyte was implanted in the can. The can was sealed, fabricating rechargeable lithium battery cell.