Disclosed is a secondary battery, comprising an electrode component, a case, a top cover component and a first insulating tape. The electrode component includes a first electrode unit. The first electrode unit is wound into a flat structure and has a first termination line formed at a winding tail-end; a negative plate of an outermost circle of the first electrode unit is located outside a positive plate of an outermost circle; and the first insulating tape at least covers a portion of the first termination line. A surface of the first electrode unit includes a first flat surface; the first flat surface is located at one end of the first electrode unit that is close to the first side wall in the thickness direction; and the first insulating tape is at least partially in close contact with the first flat surface.