An electrolyte for a lithium secondary battery comprises lithium salts, a non-aqueous organic solvent, and an additive compound of formula (1): ##STR00001## where R.sub.1 to R.sub.10 are independently selected from the group consisting of a hydrogen, alkyl, alkenyl, and alkynyl. The additive compound decomposes earlier than organic solvent to form an SEI film, and prevents decomposition of the organic solvent.