A battery according to an embodiment may comprise an electrode assembly, said electrode assembly comprising an electrode substrate comprising a first area and a second area; an active material deposited on the first area of the electrode substrate; and an electrode tab attached to the second area of the electrode substrate, wherein the electrode tab comprises a bonding surface having at least one protrusion making contacting with a bonding location of the second area of the electrode substrate, wherein a surface opposite to the bonding surface and a surface opposite the bonding location are substantially flat.