A tab for use in a battery comprises a metal piece that comprises a cross-sectional area geometry that is a rhombus, a parallelogram or a trapezoid when viewed in a lateral direction. The metal piece further comprises a cross-sectional area geometry having a variable thickness when viewed in a longitudinal direction that is perpendicular to the lateral direction. When viewed in the longitudinal direction, a tab thickness t1 at a point where the tab is in contact with an electrode is less than the tab thickness t2 at a point where the tab contacts a pouch.