The present invention provides a battery cell, wherein an electrode assembly having a positive electrode, a negative electrode and a separation membrane arranged between the positive electrode and the negative electrode is built in a battery case. The electrode assembly includes two or more unit cells that are vertically stacked relative to a plane and have different plane sizes, wherein one or more unit cells (a) of the unit cells have an asymmetric structure formed on one or more sides of an outer circumference surface relative to a central axis crossing the main body of the unit cells (a); and one or more unit cells (b) of the unit cells have an indented part that is indented from one or more side surfaces of the unit cell (b) towards the centre of the unit cell (b).