Patent ID: 8168320

Claim:
A secondary battery comprising: a spirally wound electrode body in which a cathode having a cathode active material layer on a strip-shaped cathode current collector and an anode having an anode active material layer on a strip-shaped anode current collector are layered with a separator in between, and spirally wound in a planular state; and a lead joined to the cathode current collector in a center portion of the spirally wound electrode body, wherein, the anode active material layer includes at least one of tin (Sn) and silicon (Si), a spirally winding center side end of the cathode active material layer is provided in a region where the spirally winding center side end does not overlap with the cathode lead in a short axis direction of the spirally wound electrode body, a spirally winding center side of the anode active material layer is provided in a region where the spirally winding center side end overlaps with the cathode lead in a short axis direction of the spirally wound electrode body, and the spirally wound electrode body is structured so that the spirally winding center side end and a spirally winding outer circumferential side end of the cathode active material layer and the spirally winding center side end of the anode active material layer are located on one side of two regions divided by a long axis, and a flat portion having the spirally winding center side end of the cathode active material layer and a flat portion having the spirally winding outer circumferential side end of the cathode active material layer do not overlap with each other in a short axis direction.