Lithium Secondary Battery

Abstract: The present invention provides a lithium secondary battery comprising: a negative electrode; a positive electrode facing the negative electrode; a separator disposed between the negative electrode and the positive electrode; and a non-aqueous electrolyte. The negative electrode comprises a negative active material, and the negative active material comprises a silicon-based active material. The non-aqueous electrolyte comprises a lithium salt, an organic solvent, and an additive, and the additive comprises a first additive and a second additive. The first additive comprises a coumarin-based compound represented by a specific chemical formula, and the second additive comprises at least one selected from the group consisting of lithium fluoromalonato(difluoro)borate (LiFMDFB), lithium difluoro(oxalato)borate (LiDFOB), lithium difluorophosphate (LiDFP), and lithium difluorobis-(oxalate)phosphate (LiDFOP). In the secondary battery according to the present invention, a flexible film having excellent durability is formed on the negative electrode comprising a silicon-based active material, thus improving high-temperature cycle characteristics and high-temperature storage characteristics.

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