A lithium secondary battery that has a battery cell structure, with improved electrochemical stability between an electrode and an electrolyte. In addition, the lithium secondary battery improves ion conductivity while applying a solid electrolyte. More specifically, a lithium secondary battery comprising a separator formed by an electrolyte between the cathode and the anode, wherein a composite coated layer of lithium-lanthanum-titanate (LixLayTiO3) and lithium-lanthanum-zirconium-oxide (Li7La3Zr2O12) is formed on the interface of the anode and the electrolyte.