The present invention relates to a lithium secondary battery comprising a non-aqueous liquid electrolyte comprising lithium bis(fluorosulfonyl)imide (LiFSI) and a fluorinated ether 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. According to a non-aqueous liquid electrolyte for a lithium secondary battery of the present invention, a rigid SEI layer may be formed at a negative electrode during the initial charging of the lithium secondary battery comprising the same, the output properties of the lithium secondary battery may be improved, and the output properties after storing at high temperature and capacity properties may be increased.