An electrolyte for a lithium secondary battery includes lithium salts, a
non-aqueous organic solvent, and additive compounds. The additive
compounds added to the electrolyte of the present invention decompose
earlier than the organic solvent to form a conductive polymer layer on
the surface of a positive electrode, and prevent decomposition of the
organic solvent. Accordingly, the electrolyte inhibits gas generation
caused by decomposition of the organic solvent at initial charging, and
thus reduces an increase of internal pressure and swelling during high
temperature storage, and also improves safety of the battery during
overcharge.