CELL, ELECTRODE, AND COLLECTOR USED IN THEM

摘要

Provided is a collector including a base portion having a flat surface, a first protrusion protruding from the flat surface, and a second protrusion protruding from the top of the first protrusion. Moreover, the top of the first protrusion has a ratio of an apparent area of a predetermined region of the top of the first protrusion against a surface area of the predetermined region within a range from 3 to 20. By using such a collector, it is possible to suppress peeling off of an active material from a collector when the active material has a large capacity but a large expansion upon occlusion of lithium ions.