A secondary battery comprising a positive electrode current collector, a first positive electrode mixture layer disposed on the positive electrode current collector and including a first positive electrode active material and a binder, and a second positive electrode mixture layer disposed on the first positive electrode mixture layer and including a second positive electrode active material and a binder. A nickel content of the second positive electrode active material is 80% by weight or less of a nickel content of the first positive electrode active material. By providing a secondary battery including a positive electrode of a multi-layer structure that includes positive electrode active materials having different contents of nickel, a secondary battery capable of improving high-temperature characteristics while maintaining energy density may be provided.