Patent ID: 7955730

Claim:
A battery comprising: a housing; an electrode assembly enclosed in the housing, the electrode assembly comprising a first electrode sheet, a second electrode sheet and at least one separator, which are rolled together generally about an axis to form a roll, the at least one separator being dielectrically interposed between the first and second electrode sheets in the roll; and a core placed in the center of the roll, the core comprising a substantially tubular-shaped wall surrounding the axis, the tubular-shaped wall comprising an outer surface facing the roll and an inner surface facing the axis, the inner surface defining a circumference, the core comprising at least one reinforcing structure formed in the tubular-shaped wall, the reinforcing structure being elongated in a direction extending along the axis; wherein the at least one reinforcing structure comprises at least one wrinkle in the wall, wherein the at least one wrinkle comprises a recess on the outer surface and a bulge on the inner surface; wherein the substantially tubular-shaped wall comprises a first edge extending along the axis and a second edge extending along the axis, wherein the first and second edges generally face each other with a gap therebetween, and wherein the bulge is substantially diametrically opposing the gap with respect to the central axis.