An electrode stack comprising: at least one positive electrode ; at least one negative electrode ; and at least one separator including a first separator and a second separator, wherein the positive electrode , the negative electrode , and the first separator are stacked such that the at least one separator is disposed between the positive electrode and the negative electrode , wherein one end of each of the positive electrode and the negative electrode does not overlap the other end of each of the positive electrode and the negative electrode , wherein a stacked surface of each of the positive electrode , the negative electrode , and the at least one separator comprises a curved surface, wherein the negative electrode has an arc length greater than that of the positive electrode while the at least one separator has an arc length greater than that of the positive electrode in a state in which the positive electrode , the negative electrode , and the at least one separator are curved, wherein the negative electrode has a length equivalent to 1.1 to 1.3 times that of the positive electrode , wherein a side surface of the electrode stack that is not parallel to the stacked surface comprises one or more non-curved surfaces, wherein electrode tabs are formed at the non-curved surfaces, wherein one end of the first separator does not overlap the other end of the first separator, wherein the second separator wraps side surfaces of the electrodes , at which no electrode tabs are formed, wherein the second separator differs from the first separator in that one end of the second separator overlaps the other end of the second separator. at least one positive electrode ; at least one negative electrode ; and at least one separator including a first separator and a second separator, wherein the positive electrode , the negative electrode , and the first separator are stacked such that the at least one separator is disposed between the positive electrode and the negative electrode , wherein one end of each of the positive electrode and the negative electrode does not overlap the other end of each of the positive electrode and the negative electrode , wherein a stacked surface of each of the positive electrode , the negative electrode , and the at least one separator comprises a curved surface, wherein the negative electrode has an arc length greater than that of the positive electrode while the at least one separator has an arc length greater than that of the positive electrode in a state in which the positive electrode , the negative electrode , and the at least one separator are curved, wherein the negative electrode has a length equivalent to 1.1 to 1.3 times that of the positive electrode , wherein a side surface of the electrode stack that is not parallel to the stacked surface comprises one or more non-curved surfaces, wherein electrode tabs are formed at the non-curved surfaces, wherein one end of the first separator does not overlap the other end of the first separator, wherein the second separator wraps side surfaces of the electrodes , at which no electrode tabs are formed, wherein the second separator differs from the first separator in that one end of the second separator overlaps the other end of the second separator. <EOS>