A non-aqueous electrolyte solution comprising: a 1.2 M to 3.3 M lithium salt, a first organic solvent composed of ethylene carbonate, a second organic solvent excluding the ethylene carbonate, and an oligomer represented by Formula 1 as a first additive, wherein the first organic solvent is included in an amount of 0.1 wt% to 12 wt% based on a total weight of the non-aqueous electrolyte solution, and wherein the non-aqueous electrolyte solution further comprises at least one compound selected from the group consisting of a fluorine-containing aromatic compound having 9 or less carbon atoms, a carbonate ester compound having an unsaturated bond, and an acid anhydride: wherein, in Formula 1, R 1 is an alkylene group having 1 to 5 carbon atoms which is unsubstituted or substituted with at least one fluorine element or R 1 '-O-, wherein R 1 ' is an alkylene group having 1 to 5 carbon atoms which is unsubstituted or substituted with at least one fluorine element, R 2 is an alkylene group having 1 to 5 carbon atoms which is unsubstituted or substituted with at least one fluorine element or R 2 '-O-, wherein R 2 ' is an alkylene group having 1 to 5 carbon atoms which is unsubstituted or substituted with at least one fluorine element, R 3 is an alkylene group having 1 to 5 carbon atoms which is unsubstituted or substituted with at least one fluorine element or R 3 '-O-, wherein R 3 ' is an alkylene group having 1 to 5 carbon atoms which is unsubstituted or substituted with at least one fluorine element, R 4 is an aliphatic hydrocarbon group or an aromatic hydrocarbon group, R a and R b are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms, m and n are each independently an integer of 1 to 5, and a and b are each independently an integer of 1 to 3. a 1.2 M to 3.3 M lithium salt, a first organic solvent composed of ethylene carbonate, a second organic solvent excluding the ethylene carbonate, and an oligomer represented by Formula 1 as a first additive, wherein the first organic solvent is included in an amount of 0.1 wt% to 12 wt% based on a total weight of the non-aqueous electrolyte solution, and wherein the non-aqueous electrolyte solution further comprises at least one compound selected from the group consisting of a fluorine-containing aromatic compound having 9 or less carbon atoms, a carbonate ester compound having an unsaturated bond, and an acid anhydride: wherein, in Formula 1, R 1 is an alkylene group having 1 to 5 carbon atoms which is unsubstituted or substituted with at least one fluorine element or R 1 '-O-, wherein R 1 ' is an alkylene group having 1 to 5 carbon atoms which is unsubstituted or substituted with at least one fluorine element, R 2 is an alkylene group having 1 to 5 carbon atoms which is unsubstituted or substituted with at least one fluorine element or R 2 '-O-, wherein R 2 ' is an alkylene group having 1 to 5 carbon atoms which is unsubstituted or substituted with at least one fluorine element, R 3 is an alkylene group having 1 to 5 carbon atoms which is unsubstituted or substituted with at least one fluorine element or R 3 '-O-, wherein R 3 ' is an alkylene group having 1 to 5 carbon atoms which is unsubstituted or substituted with at least one fluorine element, R 4 is an aliphatic hydrocarbon group or an aromatic hydrocarbon group, R a and R b are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms, m and n are each independently an integer of 1 to 5, and a and b are each independently an integer of 1 to 3.