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

A rechargeable lithium battery, comprising:

• a positive electrode;
• a negative electrode;
• and
• an electrolyte including:
• a lithium salt,
• a silylborate-based compound (A) represented by Formula 1:
• wherein, in Formula 1, R1 to R9 are each independently hydrogen, a halogen-substituted C1 to C10 alkyl, or an unsubstituted C1 to C10 alkyl,
• an anhydride component (B) consisting of one or more compounds represented by Formulae 2 to 5:
• wherein, in Formulae 2 to 5, R10 to R25 are each independently hydrogen or a C1 to C10 alkyl, and
• a non-aqueous organic solvent, wherein:
• the silylborate-based compound (A) and the anhydride component (B) are included at a weight ratio (A/B) of about 0.1 to 0.5 or 2 to about 15,
• the silylborate-based compound (A) is included in an amount of about 0.05 to about 3 wt % based on the combined weight of the non-aqueous organic solvent and the lithium salt, and
• the anhydride component (B) is included in an amount of about 0.3 to about 3 wt % based on the combined weight of the non-aqueous organic solvent and the lithium salt,
• wherein:
• the organic solvent includes about 15 to about 25 volume % of a cyclic carbonate and the electrolyte has a viscosity of about 3.0 to about 3.7 cP at 0° C., or
• the organic solvent includes about 26 to about 35 volume % of a cyclic carbonate and the electrolyte has a viscosity of about 4.0 to about 4.7 cP at 0° C.