Disclosed herein is a battery cell configured to have a structure in which two or more electrode assemblies, each including positive electrodes, negative electrodes, and separators disposed respectively between the positive electrodes and the negative electrodes, are mounted in a battery case, wherein the electrode assemblies are stacked such that electrode terminals of the electrode assemblies are aligned in a vertical direction, one side lower edge of an upper one of the electrode assemblies is disposed in contact with a top surface of a lower one of the electrode assemblies, and one side upper edge of the lower electrode assembly is disposed in contact with a bottom surface of the upper electrode assembly at an interface between the electrode assemblies, and the battery case has an internal shape corresponding to an external shape of the stacked electrode assemblies.