Provided is a non-aqueous electrolyte solution including a non-aqueous organic solvent, an imide-based lithium salt, and at least one additive selected from the group consisting of lithium difluoro bis(oxalato)phosphate (LiDFOP), (trimethylsilyl)propyl phosphate (TMSPa), 1,3-propene sultone (PRS), and ethylene sulfate (ESa), as an electrolyte solution additive.According to the electrolyte solution additive for a lithium secondary battery of the present invention, the electrolyte solution additive may improve output characteristics at high and low temperatures and may prevent a swelling phenomenon by suppressing the decomposition of PF6− on the surface of a cathode, which may occur during a high-temperature cycle of a lithium secondary battery including the electrolyte solution additive, and preventing an oxidation reaction of an electrolyte solution.