A secondary battery and a preparation method thereof, and a battery module, battery pack, and apparatus containing a secondary battery are provided. In some embodiments, the secondary battery includes a positive electrode plate, a negative electrode plate, and an electrolyte, where the positive electrode plate includes a positive electrode current collector and a positive electrode film layer that is disposed on at least one surface of the positive electrode current collector and that includes a positive electrode active material, and the negative electrode plate includes a negative electrode current collector and a negative electrode film layer that is disposed on at least one surface of the negative electrode current collector and that includes a negative electrode active material; and the positive electrode active material includes a first material and a second material.