Non-aqueous electrolyte solution and lithium secondary battery including the same

A non-aqueous electrolyte solution comprising:

• a lithium salt;
• a first organic solvent that is ethylene carbonate;
• a second organic solvent excluding ethylene carbonate;
• and
• an oligomer represented by Formula 1,
• wherein the lithium salt is present in a concentration of 1.2 M to 3.3 M, and
• 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:
• wherein, in Formula 1,
• R1 is an alkylene group having 1 to 5 carbon atoms which is substituted with at least one fluorine or R1′—O—, wherein R1′ is an alkylene group having 1 to 5 carbon atoms which is substituted with at least one fluorine,
• R2 is an alkylene group having 1 to 5 carbon atoms which is substituted with at least one fluorine or R2′—O—, wherein R2′ is an alkylene group having 1 to 5 carbon atoms which is substituted with at least one fluorine,
• R3 is an alkylene group having 1 to 5 carbon atoms which is substituted with at least one fluorine or R3′—O—, wherein R3′ is an alkylene group having 1 to 5 carbon atoms which is substituted with at least one fluorine,
• R4 is an aliphatic hydrocarbon group or an aromatic hydrocarbon group,
• Ra and Rb 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.