NOVELTY - An electrolyte composition comprises aprotic organic solvent, conducting salt, dicarbonitrile compound (I) and additive.    USE - Electrolyte composition for use in electrochemical cells that is secondary lithium ion battery. (all claimed) that is utilized in mobile devices, vehicles, automobiles, bicycles, aircraft, or water vehicles such as boats or ships, computers, laptops, telephones or electrical power tools, construction sector, especially drills, battery-driven screwdrivers or battery-driven staplers and stationary energy stores.    ADVANTAGE - The composition has prolonged life time, cycle stability, high energy density, high operating voltage, and good performance characteristics of the battery.    DETAILED DESCRIPTION - An electrolyte composition comprises aprotic organic solvent, conducting salt, dicarbonitrile compound of formula (I) and additive.    X1, X2 = N(R1), N=C(R2) P(R1), O or S;    R1 = 1-10C alkyl, 3-6C (hetero)cycloalkyl, 2-10C alkenyl, 3-6C (hetero)cycloalkenyl, 2-6C alkynyl, 5-7C (hetero)aryl, 7-13C aralkyl (all optionally substituted with substituents selected from F, CN, 1-6C alkyl, 3-6C (hetero)cycloalkyl, 2-6C alkenyl, 5-7C (hetero)aryl, S(O)2OR3a, OS(O)2R3a, S(O)2R3a, OR3a, C(O)R3a, C(O)OR3a, NR3aR3b, or NC(O)R3aR3b), H, OR3, C(O)R3, C(NR3)R4 or C(O)OR3;    R2 = 1-10C alkyl, 3-6C (hetero)cycloalkyl, 2-10C alkenyl, 3-6C (hetero)cycloalkenyl, 2-6C alkynyl, 5-7C (hetero)aryl, 7-13C aralkyl (all optionally substituted with substituents selected from F, CN, 1-6C alkyl, 3-6C (hetero)cycloalkyl, 2-6C alkenyl, 5-7C (hetero)aryl, S(O)2OR3a, OS(O)2R3a, S(O)2R3a, OR3a, C(O)R3a, C(O)OR3a, NR3aR3b, or NC(O)R3aR3b), H, CN, F, S(O)2OR3, OS(O)2R3, S(O)2R3, OR3, C(O)R3, C(NR3)R4, C(O)OR3, NR3R4, NC(O)R3, P(O)R3R4, or SiR3R4R5;    R3, R4, R5, R3a, R3b = 1-10C alkyl, 3-6C (hetero)cycloalkyl, 2-10C alkenyl, 3-6C (hetero)cycloalkenyl, 2-6C alkynyl, 5-7C (hetero)aryl, 7-13C aralkyl (all optionally substituted with substituents selected from F, CN, 1-6C alkyl, 3-6C (hetero)cycloalkyl, 2-6C alkenyl, 5-7C (hetero)aryl, S(O)2OR3c, OS(O)2R3c, S(O)2R3c, OR3c, O(O)R3c, O(O)OR3c, NR3cR3d, or NC(O)R3cR3d) or H;    A1, A2 = 1-10C alkyl, 3-6C (hetero)cycloalkyl, 2-10C alkenyl, 3-6C (hetero)cycloalkenyl, 2-6C alkynyl, 5-7C (hetero)aryl, 7-13C aralkyl (all optionally substituted with substituents selected from F, CN, 1-6C alkyl, 3-6C (hetero)cycloalkyl, 2-6C alkenyl, 5-7C (hetero)aryl, S(O)2OR6a, OS(O)2R6a, S(O)2R6a, OR6a, C(O)OR6a, NR6aR6b and/or NC(O)R6aR6b), OR6, C(O)R6, C(NR6)R7 or C(O)OR6, Provided that in case of X2 is O or S, A2 is neither H nor OR6;    R6, R7, R6a, R6b = 1-10C alkyl, 3-6C (hetero)cycloalkyl, 2-10C alkenyl, 3-6C (hetero)cycloalkenyl, 2-6C alkynyl, 5-7C (hetero)aryl and 7-13C aralkyl (all optionally substituted with substituents selected from F, CN, 1-6C alkyl, 3-6C (hetero)cycloalkyl, 2-6C alkenyl, 5-7C (hetero)aryl, S(O)2OR6c, OS(O)2R6c, S(O)2R6c, OR6c, C(O)R6c, C(O)OR6c, NR6cR6d and/or NC(O)R6cR6d) or H R3c; and    R3d, R6c, R6d = 1-10C alkyl, 3-6C (hetero)cycloalkyl, 2-6C alkenyl, 5-7C (hetero)aryl (all optionally substituted with substituents selected from F or CN) or H.    INDEPENDENT CLAIMS are also included for the following:    (1) an use of dicarbonitrile compound (I) as additive for electrolytes in electrochemical cell    (2) an electrochemical cell comprising electrolyte composition, cathode comprising cathode active material, and anode comprising anode active material.