Disclosed herein is a battery cell including an electrode assembly of a cathode/separator/anode structure mounted in a receiving part of a battery case (cell case). The cell case is provided, at a predetermined region of the cell case corresponding to the upper end interface of the electrode assembly while the electrode assembly is mounted in the receiving part, with a small groove for pressing against the upper end of the electrode assembly to prevent the upward movement of the electrode assembly. The small groove is continuously formed in parallel with the upper end of the electrode assembly.