The present invention provides a lithium secondary battery comprising a non-aqueous liquid electrolyte comprising lithium bis(fluorosulfonyl)imide (LiFSI) and a fluorinated benzene-based compound as additives, a positive electrode comprising a lithium-nickel-manganese-cobalt-based oxide as a positive electrode active material, a negative electrode, and a separator. With the non-aqueous liquid electrolyte for a lithium secondary battery of the present invention, a solid SEI film is formed on a negative electrode when initially charging a lithium secondary battery comprising the non-aqueous liquid electrolyte, and an output property of the lithium secondary battery is improved, and an output property and stability after high temperature storage are capable of being enhanced as well.