SECONDARY BATTERY

The present invention addresses the problems that a mixture-layer-coatless region, which is an attachment base for tab portions, sags in a large manner, and that suppression effect is small in terms of the sagging amount for the entirety of the tab portions. Negative electrode tabs 17 are arranged into a single body with a negative electrode mixture-layer-coatless region 12c, on a negative electrode metal foil 12a from a negative pole electrode 12, at a predetermined pitch along one side edge 61 of the negative electrode metal foil 12a in the length direction thereof. The mixture-layer-coatless region 12c comprises valley-fold portions 50 (deformed reinforcement portions), a depression being formed in each. By having a shape comprising valley-fold portions 50, the rigidity of the negativeelectrode mixture-layer-coatless region 12c is large compared to that of a planar shape having no valley-fold portion 50, leading to a small sagging angle caused by gravity, or the like, for the negative electrode mixture-lay