Electrolyte for rechargeable lithium battery and rechargeable lithium battery including the same

A rechargeable lithium battery, comprising:

• a positive electrode comprising a positive active material;
• a negative electrode comprising a negative active material comprising a Si-based active material selected from the group consisting of:
• Si;
• SiOx wherein 0<x<2;
• Si—Y alloys wherein Y is an element selected from the group consisting of alkali metals, alkaline-earth metals, group 13 through group 16 elements, transition elements, rare earth elements, and combinations thereof, but Y is not Si;
• carbon-coated SiOx wherein 0<x<2;
• Si—C composites;
• and
• combinations thereof;
• and
• an electrolyte comprising:
• a non-aqueous organic solvent;
• a lithium salt;
• and
• an additive comprising a compound represented by Chemical Formula 1:
• wherein:
• each of X1 and X2 is independently a halogen or hydrogen, provided that at least one of X1 and X2 is F,
• each of R1 through R3 is hydrogen, and
• R4 is selected from the group consisting of unsubstituted butyl groups, and unsubstituted hexyl groups.