TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - The content of lithium salt (B) and content of cyclic compound is 0.1-10 wt.% (preferably 0.75-2 wt.%) and 0.005-3 wt.% (preferably 0.03-0.1 wt.%), with respect to total weight of the electrolyte. The concentration of lithium salt (A) is 0.8-1.3 M, preferably 1-1.2 M. The lithium salt (A) is chosen from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroborate, lithium hexafluoroantimonate, lithium hexafluoroarsenate, lithium trifluoromethane sulfonate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(pentafluoroethanesufonyl)imide, lithium perchlorate, lithium aluminate and lithium tetrachloroaluminate. The weight ratio of lithium salts (A) and (B) is 1:9-9:1, preferably 1:3-3:1. The weight ratio of cyclic compound and lithium salt (B) is 0.005:1-1:1, preferably 0.05:1-0.3:1. The nonaqueous solvent(s) is linear carbonate compound(s), cyclic carbonate compound(s), ester-based compound(s), ether-based compound(s) and/or ketone-based compound(s), preferably, diethyl carbonate, ethylmethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, methylethyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, fluoroethylene carbonate and/or vinylethylene carbonate, and comprises mixture of linear carbonate(s) (50-99 wt.%, preferably 60-80 wt.%) and cyclic carbonate(s) (1-50 wt.%, preferably 20-40 wt.%), with respect to total amount of nonaqueous organic solvent. The cyclic compound(s) is chosen from thiophene, furan, 2,3-dihydrothieno(3,4-b)(1,4)dioxine and 1-methyl-1H-pyrrole, preferably thiophene or 1-methyl-1H-pyrrole. The lithium salt(s) (B) is lithium 2,2-difluoro-1,3,2-dioxaborolane-4,5-dione and/or lithium 1,4,6,9-tetraoxa-5-boraspiro(4.4)nonane-2,3,7,8-tetrone, and lithium 5,5-difluoro-1,4,6,9-tetraoxa-5-phosphaspiro(4.4)nonane-2,3,7,8-tetrone, lithium 2,2,2,2-tetrafluoro-1,3,2-dioxaphospholane-4,5-dione and/or lithium oxophosphonoyl difluoride, preferably lithium 2,2-difluoro-1,3,2-dioxaborolane-4,5-dione. Preferred Definitions:    at least one of R1/R2+R3/R4=5-membered ring;    l,n=1;    R13-R16=H;and    or R14+R15=six-membered ring.