Lithium Secondary Battery with Improved Safety

An electrolyte composition and a lithium secondary battery including the same are disclose herein. The electrolyte composition has improved high temperature safety. In some embodiments, the electrolyte composition includes an additive including a compound represented by Formula 1. Each Ris independently a single bond, an alkylene group having 1 to 10 carbon atoms, or each Ris independently a double or triple bond including 2 carbon atoms, each Ris independently hydrogen or an alkyl group having 1 to 4 carbon atoms, and a is an integer of 1 to 10. The additive may reinforce an SEI layer on the surface of an electrode, thereby having advantages of improved storage and lifetime characteristics at a high temperature and a decreased amount of gas generated in the battery.