An electrolyte for a rechargeable lithium battery comprising: a non-aqueous organic solvent; a lithium salt; and an electrolyte additive which is a compound represented by chemical formula 1: (R 1 O) 2 P(NR 2 R 3) Formula 1 wherein, R 1 to R 3 are each independently hydrogen, a substituted or unsubstituted C1 to C20 alkyl group, a substituted or unsubstituted C1 to C20 haloalkyl group, a substituted or unsubstituted C1 to C20 alkenyl group, a substituted or unsubstituted C2 to C20 haloalkenyl group, a substituted or unsubstituted C2 to C20 alkynyl group, a substituted or unsubstituted C2 to C20 haloalkynyl group, a substituted or unsubstituted C6 to C30 aryl group, a substituted or unsubstituted C6 to C30 haloaryl group, or -C-O-R 4, each of two R 1 is the same or different from each other, R 4 is a substituted or unsubstituted C1 to C20 alkyl group, a substituted or unsubstituted C1 to C20 haloalkyl group, a substituted or unsubstituted C6 to C30 aryl group, or a substituted or unsubstituted C6 to C30 haloaryl group; wherein the term 'substituted' refers to substituted with a substituent selected from a halogen, a hydroxyl group, an alkoxy group, a nitro group, a cyano group, an amino group, an azido group, an amidino group, a hydrazino group, a hydrazono group, a carbonyl group, a carbamyl group, a thiol group, an ester group, a carboxyl group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C1 to C20 alkyl group, a C2 to C20 alkenyl group, a C2 to C20 alkynyl group, a C6 to C30 aryl group, a C7 to C30 arylalkyl group, a C1 to C4 alkoxy group, a C1 to C20 heteroalkyl group, a C3 to C20 hetero arylalkyl group, a C3 to C30 cycloalkyl group, a C3 to C15 cycloalkenyl group, a C6 to C15 cycloalkynyl group, a C2 to C20 heterocycloalkyl group, and a combination thereof, instead of hydrogen of a compound. a non-aqueous organic solvent; a lithium salt; and an electrolyte additive which is a compound represented by chemical formula 1: (R 1 O) 2 P(NR 2 R 3) Formula 1 wherein, R 1 to R 3 are each independently hydrogen, a substituted or unsubstituted C1 to C20 alkyl group, a substituted or unsubstituted C1 to C20 haloalkyl group, a substituted or unsubstituted C1 to C20 alkenyl group, a substituted or unsubstituted C2 to C20 haloalkenyl group, a substituted or unsubstituted C2 to C20 alkynyl group, a substituted or unsubstituted C2 to C20 haloalkynyl group, a substituted or unsubstituted C6 to C30 aryl group, a substituted or unsubstituted C6 to C30 haloaryl group, or -C-O-R 4, each of two R 1 is the same or different from each other, R 4 is a substituted or unsubstituted C1 to C20 alkyl group, a substituted or unsubstituted C1 to C20 haloalkyl group, a substituted or unsubstituted C6 to C30 aryl group, or a substituted or unsubstituted C6 to C30 haloaryl group; wherein the term 'substituted' refers to substituted with a substituent selected from a halogen, a hydroxyl group, an alkoxy group, a nitro group, a cyano group, an amino group, an azido group, an amidino group, a hydrazino group, a hydrazono group, a carbonyl group, a carbamyl group, a thiol group, an ester group, a carboxyl group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C1 to C20 alkyl group, a C2 to C20 alkenyl group, a C2 to C20 alkynyl group, a C6 to C30 aryl group, a C7 to C30 arylalkyl group, a C1 to C4 alkoxy group, a C1 to C20 heteroalkyl group, a C3 to C20 hetero arylalkyl group, a C3 to C30 cycloalkyl group, a C3 to C15 cycloalkenyl group, a C6 to C15 cycloalkynyl group, a C2 to C20 heterocycloalkyl group, and a combination thereof, instead of hydrogen of a compound. R 1 to R 3 are each independently hydrogen, a substituted or unsubstituted C1 to C20 alkyl group, a substituted or unsubstituted C1 to C20 haloalkyl group, a substituted or unsubstituted C1 to C20 alkenyl group, a substituted or unsubstituted C2 to C20 haloalkenyl group, a substituted or unsubstituted C2 to C20 alkynyl group, a substituted or unsubstituted C2 to C20 haloalkynyl group, a substituted or unsubstituted C6 to C30 aryl group, a substituted or unsubstituted C6 to C30 haloaryl group, or -C-O-R 4, each of two R 1 is the same or different from each other, R 4 is a substituted or unsubstituted C1 to C20 alkyl group, a substituted or unsubstituted C1 to C20 haloalkyl group, a substituted or unsubstituted C6 to C30 aryl group, or a substituted or unsubstituted C6 to C30 haloaryl group; wherein the term 'substituted' refers to substituted with a substituent selected from a halogen, a hydroxyl group, an alkoxy group, a nitro group, a cyano group, an amino group, an azido group, an amidino group, a hydrazino group, a hydrazono group, a carbonyl group, a carbamyl group, a thiol group, an ester group, a carboxyl group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C1 to C20 alkyl group, a C2 to C20 alkenyl group, a C2 to C20 alkynyl group, a C6 to C30 aryl group, a C7 to C30 arylalkyl group, a C1 to C4 alkoxy group, a C1 to C20 heteroalkyl group, a C3 to C20 hetero arylalkyl group, a C3 to C30 cycloalkyl group, a C3 to C15 cycloalkenyl group, a C6 to C15 cycloalkynyl group, a C2 to C20 heterocycloalkyl group, and a combination thereof, instead of hydrogen of a compound.