A pouch type battery cell includes an electrode assembly having a first electrode plate, a second electrode plate, and a separator located between the first and second electrode plates; a first case having a first accommodating portion in which at least one portion of the electrode assembly is accommodated, wherein the first accommodating portion is generally concave; and a second case covering the first case, wherein the first case includes a metal layer including steel or hard aluminum, and wherein a depth of the first accommodating portion is between about 1 mm and about 4 mm, and wherein a thickness of the metal layer is between about 40 μm and about 100 μm.