A
lithium secondary battery includes a negative
electrode, a positive
electrode disposed opposite the negative
electrode, a separator disposed between the negative electrode and the positive electrode, and a non-
aqueous electrolyte. The negative electrode includes a negative electrode active material, and the negative electrode active material includes a
silicon-based active material. The non-
aqueous electrolyte includes a
lithium salt, an
organic solvent, and additives, the additives include a first additive and a second additive, the first additive includes a
coumarin-based compound represented by a specific formula, and the second additive includes at least one of
lithium fluoromalonate (difluoro) borate (LiFMDFB), lithium difluoro (
oxalate) borate (LiDFOB), lithium
difluorophosphate (LiDFP), or lithium difluoro bis (
oxalate)
phosphate (LiDFOP). In the lithium secondary battery of the present invention, a highly durable flexible film is formed on a negative electrode containing a
silicon-based active material, thereby improving high-temperature cycle life performance and high-temperature storage performance.