An electrode assembly comprising: a plurality of first polar plates comprising a first coated portion coated with a first active material and a first non-coated portion that is bent; a plurality of second polar plates comprising a second coated portion coated with a second active material and a second non-coated portion that is bent; and a plurality of separators that are interposed between the first polar plates and the second polar plates wherein each first non-coated portion comprises: a first extension portion that extends away from a first coated portion, a bending portion that is bent back towards the first coated portion, and a second extension portion that is bent again so as to extend away from the first coated portion, and wherein the second extension portion of a first non-coated portion is arranged to be adjacent to the first extension portion of an adjacent first non-coated portion, and wherein each second non-coated portion comprises: a first extension portion that extends away from a second coated portion, a bending portion that is bent back towards the second coated portion, and a second extension portion that is bent again so as to extend away from the second coated portion, and wherein the second extension portion of a second non-coated portion is arranged to be adjacent to the first extension portion of an adjacent second non-coated portion, wherein the first polar plates are arranged at a first interval (W 1) and the second polar plates are arranged at a second interval, wherein the first interval is equal to the second interval, and wherein a width (W1') of the first non-coated portion that is bent is equal to or smaller than the first interval, and a width (W2') of the second non-coated portion that is bent is equal to or smaller than the second interval. a plurality of first polar plates comprising a first coated portion coated with a first active material and a first non-coated portion that is bent; a plurality of second polar plates comprising a second coated portion coated with a second active material and a second non-coated portion that is bent; and a plurality of separators that are interposed between the first polar plates and the second polar plates wherein each first non-coated portion comprises: a first extension portion that extends away from a first coated portion, a bending portion that is bent back towards the first coated portion, and a second extension portion that is bent again so as to extend away from the first coated portion, and wherein the second extension portion of a first non-coated portion is arranged to be adjacent to the first extension portion of an adjacent first non-coated portion, and a first extension portion that extends away from a first coated portion, a bending portion that is bent back towards the first coated portion, and a second extension portion that is bent again so as to extend away from the first coated portion, and wherein the second extension portion of a first non-coated portion is arranged to be adjacent to the first extension portion of an adjacent first non-coated portion, and wherein each second non-coated portion comprises: a first extension portion that extends away from a second coated portion, a bending portion that is bent back towards the second coated portion, and a second extension portion that is bent again so as to extend away from the second coated portion, and wherein the second extension portion of a second non-coated portion is arranged to be adjacent to the first extension portion of an adjacent second non-coated portion, a first extension portion that extends away from a second coated portion, a bending portion that is bent back towards the second coated portion, and a second extension portion that is bent again so as to extend away from the second coated portion, and wherein the second extension portion of a second non-coated portion is arranged to be adjacent to the first extension portion of an adjacent second non-coated portion, wherein the first polar plates are arranged at a first interval (W 1) and the second polar plates are arranged at a second interval, wherein the first interval is equal to the second interval, and wherein a width (W1') of the first non-coated portion that is bent is equal to or smaller than the first interval, and a width (W2') of the second non-coated portion that is bent is equal to or smaller than the second interval.