Patent ID: 7976973

Claim:
A battery comprising: a cathode; an anode; and a separator in between the cathode and anode, wherein, the cathode, the anode and the separator are spirally wound to form a spirally wound electrode body, the cathode has a cathode current collector having (1) an outer face that faces away from the center of the spirally wound electrode body (2) an inner-face that faces towards the center of the spirally wound electrode body, the outer face and inner face being on opposite sides of the cathode current collector, an outer-face cathode active material layer on the outer face of the cathode current collector, an inner-face cathode active material layer on the inner face of the cathode current collector, the current collector has an exposed surface without an outer-face cathode active material and an inner-face cathode material thereon, a lead attached to the exposed surface of the current collector on a side of the current collector that faces towards the center of spirally wound electrode body, a thickness of the inner-face cathode active material layer is smaller than a thickness of the outer-face cathode active material layer, an outer face region of the spirally wound electrode body that faces the center the spirally wound electrode body, only the outer-face cathode active material layer on the outer face of the spirally wound electrode body, and wherein the porosities of the outer-face cathode active material layer and the inner-face cathode active material layer are within the range from 20% to 27%, and the outer face region overlaps the lead on the center side of the spirally wound electrode body.