Electrolyte solvent for improving safety of battery and lithium secondary battery comprising the same

The present invention provides an electrolyte solvent for batteries, which comprises fluoroethylene carbonate and linear ester solvent. Also, the present invention provides a lithium secondary battery comprising a positive electrode, a negative electrode and an electrolyte, wherein the electrolyte comprises fluoroethylene carbonate and linear ester solvent. The inventive electrolyte solvent can improve the battery safety without deteriorating the battery performance.