Secondary battery

Provided in one embodiment of the present invention is a secondary battery comprising, housed in an exterior body, an electrolyte and an electrode assembly (100A) containing a positive electrode (10A), a negative electrode (10B), and a separator (50) disposed between the positive electrode (10A) and the negative electrode (10B). In the secondary battery, the electrode assembly (100A) comprises a planar layered structure, as seen in a cross sectional view, wherein a plurality of electrode-constituting layers have been layered into a planar shape, each containing a positive electrode (10A), a negative electrode (10B) and a separator (50), and has a cut-out section (30A) as seen in a planar view. The electrode assembly (100A) is provided with securing members (60Aa, 60Ab) for securing at least a cut-out side surface (101A) of the electrode assembly (100A) forming the cut-out section (30A), and a non-cut-out side surface (102A) of the electrode assembly (100A), facing away from the cut-outside surface (101A) and