An electrode assembly includes a first electrode at an upper part, a second electrode at a lower part, and an electrolyte membrane between the first electrode and the second electrode. Each of the first electrode and the second electrode includes an electrode active material layer, a tab portion, and a non-coated portion, the non-coated portion being located at at least one lateral side of the first electrode or the second electrode, and the non-coated portion of at least one of the first electrode and the second electrode includes at least one groove that is parallel to a thickness direction of the first electrode or the second electrode.