Abstract: A secondary battery includes an electrode assembly, a packaging bag, and an insulation adhesive. The packaging bag includes a main portion and a first side seal edge. The main portion accommodates the electrode assembly, and includes a first sidewall and a second sidewall disposed along a thickness direction of the secondary battery. The first side seal edge includes a first connecting portion and a second connecting portion disposed in sequence. The first connecting portion is connected to the main portion. The second connecting portion is bent toward the main portion relative to the first connecting portion. An angle ? is formed between the first connecting portion and the first sidewall, satisfying: 0°<?<90°. A thickness of the main portion is less than a width of the first connecting portion. The insulation adhesive covers one end, facing the main portion, of the second connecting portion.