An electrolyte, comprising: a cyclic ester compound substituted with a sulfonate group; and an organic solvent, wherein the cyclic ester compound is represented by Formula 1: wherein, in Formula 1, A 1 and A 2 each independently are oxygen or sulfur, is selected from a substituted or unsubstituted C1 to C10 alkylene group or a substituted or unsubstituted C2 to C10 alkenylene group, and at least one selected from R 1 and R 2 is a sulfonate group, wherein, when only one of R 1 and R 2 is a sulfonate group, the other one of R 1 and R 2 is hydrogen, a halogen, a substituted or unsubstituted C1 to C30 alkyl group, a substituted or unsubstituted C2 to C30 alkenyl group, a substituted or unsubstituted C2 to C30 alkynyl group, a substituted or unsubstituted C3 to C30 carbocyclic group, a substituted or unsubstituted C1 to C10 alkoxy group, a substituted or unsubstituted C6 to C30 aryl group, a substituted or unsubstituted C3 to C30 cycloalkenyl group, a substituted or unsubstituted C7 to C20 arylalkyl group, a substituted or unsubstituted C1 to C10 heteroalkyl group, a substituted or unsubstituted C2 to C30 heterocyclic group, or a substituted or unsubstituted C2 to C30 heteroaryl group. a cyclic ester compound substituted with a sulfonate group; and an organic solvent, wherein the cyclic ester compound is represented by Formula 1: wherein, in Formula 1, A 1 and A 2 each independently are oxygen or sulfur, is selected from a substituted or unsubstituted C1 to C10 alkylene group or a substituted or unsubstituted C2 to C10 alkenylene group, and at least one selected from R 1 and R 2 is a sulfonate group, wherein, when only one of R 1 and R 2 is a sulfonate group, the other one of R 1 and R 2 is hydrogen, a halogen, a substituted or unsubstituted C1 to C30 alkyl group, a substituted or unsubstituted C2 to C30 alkenyl group, a substituted or unsubstituted C2 to C30 alkynyl group, a substituted or unsubstituted C3 to C30 carbocyclic group, a substituted or unsubstituted C1 to C10 alkoxy group, a substituted or unsubstituted C6 to C30 aryl group, a substituted or unsubstituted C3 to C30 cycloalkenyl group, a substituted or unsubstituted C7 to C20 arylalkyl group, a substituted or unsubstituted C1 to C10 heteroalkyl group, a substituted or unsubstituted C2 to C30 heterocyclic group, or a substituted or unsubstituted C2 to C30 heteroaryl group. A 1 and A 2 each independently are oxygen or sulfur, is selected from a substituted or unsubstituted C1 to C10 alkylene group or a substituted or unsubstituted C2 to C10 alkenylene group, and at least one selected from R 1 and R 2 is a sulfonate group, wherein, when only one of R 1 and R 2 is a sulfonate group, the other one of R 1 and R 2 is hydrogen, a halogen, a substituted or unsubstituted C1 to C30 alkyl group, a substituted or unsubstituted C2 to C30 alkenyl group, a substituted or unsubstituted C2 to C30 alkynyl group, a substituted or unsubstituted C3 to C30 carbocyclic group, a substituted or unsubstituted C1 to C10 alkoxy group, a substituted or unsubstituted C6 to C30 aryl group, a substituted or unsubstituted C3 to C30 cycloalkenyl group, a substituted or unsubstituted C7 to C20 arylalkyl group, a substituted or unsubstituted C1 to C10 heteroalkyl group, a substituted or unsubstituted C2 to C30 heterocyclic group, or a substituted or unsubstituted C2 to C30 heteroaryl group.