Disclosed herein is a battery cell configured such that an electrode assembly having a positive electrode/separator/negative electrode structure is received in an electrode assembly receiving part formed in a pouch-type battery case in a sealed state together with an electrolyte, wherein the battery case is provided with sealed parts, formed by thermally welding the outer edge of the battery case in the state in which the electrode assembly is received in the battery case together with the electrolyte, one or more recesses are formed in opposite side sealed parts adjacent to an upper end sealed part, at which electrode terminals are located, and/or a lower end sealed part in a state in which the recesses are formed from outsides of the side sealed parts toward a vertical middle axis of the battery cell so as to prevent wrinkles from being formed in the sealed parts of the battery case when the battery cell is bent, and portions of the side sealed parts in which the recesses are located are sealed at a higher sealing temperature than the remaining portions of the side sealed parts.