A stepped electrode assembly consisting of bi-cells: each being either an A-type bi-cell consisting of, in a stacked manner, two positive electrodes, a negative electrode disposed between the positive electrodes and two separators, each disposed between one of the positive electrodes and the negative electrode; or a C-type bi-cell consisting of, in a stacked manner, two negative electrodes, a positive electrode disposed between the negative electrodes and two separators, each disposed between one of the negative electrodes and the positive electrode, wherein the bi-cells form together: a first electrode stack comprising at least one first bi-cell, said first bi-cell comprising at least one positive electrode and at least one negative electrode having the same area and being alternately stacked in a vertical direction with a separator disposed therebetween; and a second bi-cell, the second bi-cell disposed on a side of the first electrode stack with a separator disposed therebetween, wherein the second bi-cell comprises a first area electrode having the same area as an electrode area of the first electrode stack and a second area electrode having an area different from the area of the first area electrode, wherein the second bi-cell is a stepped bi-cell comprising a stepped portion formed by an area difference between the first and second area electrodes, the larger of the two interfacial electrodes at which the stepped portion is formed being a negative electrode, and characterized in that at least one of the outermost electrodes of the electrode assembly is a one-side-coated electrode. each being either an A-type bi-cell consisting of, in a stacked manner, two positive electrodes, a negative electrode disposed between the positive electrodes and two separators, each disposed between one of the positive electrodes and the negative electrode; or a C-type bi-cell consisting of, in a stacked manner, two negative electrodes, a positive electrode disposed between the negative electrodes and two separators, each disposed between one of the negative electrodes and the positive electrode, wherein the bi-cells form together: a first electrode stack comprising at least one first bi-cell, said first bi-cell comprising at least one positive electrode and at least one negative electrode having the same area and being alternately stacked in a vertical direction with a separator disposed therebetween; and a second bi-cell, the second bi-cell disposed on a side of the first electrode stack with a separator disposed therebetween, wherein the second bi-cell comprises a first area electrode having the same area as an electrode area of the first electrode stack and a second area electrode having an area different from the area of the first area electrode, wherein the second bi-cell is a stepped bi-cell comprising a stepped portion formed by an area difference between the first and second area electrodes, the larger of the two interfacial electrodes at which the stepped portion is formed being a negative electrode, and characterized in that at least one of the outermost electrodes of the electrode assembly is a one-side-coated electrode. a first electrode stack comprising at least one first bi-cell, said first bi-cell comprising at least one positive electrode and at least one negative electrode having the same area and being alternately stacked in a vertical direction with a separator disposed therebetween; and a second bi-cell, the second bi-cell disposed on a side of the first electrode stack with a separator disposed therebetween, wherein the second bi-cell comprises a first area electrode having the same area as an electrode area of the first electrode stack and a second area electrode having an area different from the area of the first area electrode, wherein the second bi-cell is a stepped bi-cell comprising a stepped portion formed by an area difference between the first and second area electrodes, the larger of the two interfacial electrodes at which the stepped portion is formed being a negative electrode, and characterized in that at least one of the outermost electrodes of the electrode assembly is a one-side-coated electrode.