A lithium secondary battery including: a cathode including a high-voltage cathode active material; an anode; and an electrolyte disposed between the cathode and the anode, wherein the high-voltage cathode active material has a charge cut-off voltage of about 4.2 Volts or greater with respect to a lithium (Li) counter electrode, and wherein the electrolyte includes an organic fluorinated ether compound represented by Formula 1, an organic solvent, and a lithium salt: R1—O—CFnH2-n—R2  Formula 1 wherein, in Formula 1, R1 is a C1-C10 alkyl group, a C3-C10 cycloalkyl group, a C1-C10 fluorinated alkyl group, or a C3-C10 fluorinated cycloalkyl group; R2 is hydrogen, fluorine, a C1-C10 alkyl group, a C3-C10 cycloalkyl group, a C1-C10 fluorinated alkyl group, or a C3-C10 fluorinated cycloalkyl group; and n is 1 or 2.