Electrode assembly of stair-like structure

A lithium secondary battery comprising:

• an electrode assembly including:
• an even number of unit cells, each of the unit cells having a structure in which electrode plates having opposite polarities are stacked in a height direction on the basis of a plane in a state in which a separator plate is disposed between the electrode plates, an uppermost electrode plate and a lowermost electrode plate have the same polarity, and electrode tabs protrude from the electrode plates, and
• a single, monolithic sheet type separation film to cover one major surface, another major surface, and sides of each of the unit cells, which constitute an electrode tab non-formation region,
• wherein the unit cells are stacked in the height direction on the basis of the plane such that the electrode plates having opposite polarities face each other in a state in which the separation film is disposed between the electrode plates,
• wherein at least two of the stacked unit cells have different sizes, whereby the electrode assembly has a stair-like structure, and
• wherein the separation film is disposed in contact with the major surface, the another major surface, and the sides of each of the unit cells,
• wherein the electrode assembly is mounted in a battery case in a sealed state such that the electrode assembly is impregnated with an electrolyte.