The present disclosure provides a secondary battery, which includes an electrode assembly, a case, a cap assembly and a first insulating tape. The electrode assembly comprises an electrode unit. The electrode unit comprises a positive electrode plate, a negative electrode plate and a separator. The electrode unit is a winding structure and in a flat shape, and an outermost turn of the negative electrode plate is positioned at an outer side of an outermost turn of the positive electrode plate. The case comprises a first side wall and an accommodating cavity, the electrode assembly is accommodated in the accommodating cavity, the case is electrically connected with the positive electrode plate, and the cap assembly is connected with the case. The first insulating tape is positioned between the electrode assembly and the first side wall and closely attached to an outer surface of the electrode assembly.