A battery, comprising: an electrode assembly; a case housing the electrode assembly; and a cap plate for sealing the case housing the electrode assembly, the cap plate comprising: a cover portion that covers the electrode assembly; a support portion having a first thickness, the support portion being offset along a first direction from the cover portion; and a reinforcing portion that connects the cover portion and the support portion, the reinforcing portion having a processing thickness (Tr) that is greater than the first thickness, the first thickness and the processing thickness (Tr) being measured along the first direction, wherein the reinforcing portion extends diagonally between the cover portion and the support portion wherein the reinforcing portion is arranged between the cover portion and the supporting portion characterized in that the support portion is disposed to face an inner surface of the case and wherein the support portion is secured to the inner surface of the case such that the cap plate is located lower than an upper end surface of the case and wherein the reinforcing portion extends along an entire periphery of the cover portion. an electrode assembly; a case housing the electrode assembly; and a cap plate for sealing the case housing the electrode assembly, the cap plate comprising: a cover portion that covers the electrode assembly; a support portion having a first thickness, the support portion being offset along a first direction from the cover portion; and a reinforcing portion that connects the cover portion and the support portion, the reinforcing portion having a processing thickness (Tr) that is greater than the first thickness, the first thickness and the processing thickness (Tr) being measured along the first direction, wherein the reinforcing portion extends diagonally between the cover portion and the support portion wherein the reinforcing portion is arranged between the cover portion and the supporting portion characterized in that the support portion is disposed to face an inner surface of the case and wherein the support portion is secured to the inner surface of the case such that the cap plate is located lower than an upper end surface of the case and wherein the reinforcing portion extends along an entire periphery of the cover portion. a cover portion that covers the electrode assembly; a support portion having a first thickness, the support portion being offset along a first direction from the cover portion; and a reinforcing portion that connects the cover portion and the support portion, the reinforcing portion having a processing thickness (Tr) that is greater than the first thickness, the first thickness and the processing thickness (Tr) being measured along the first direction, wherein the reinforcing portion extends diagonally between the cover portion and the support portion wherein the reinforcing portion is arranged between the cover portion and the supporting portion characterized in that the support portion is disposed to face an inner surface of the case and wherein the support portion is secured to the inner surface of the case such that the cap plate is located lower than an upper end surface of the case and wherein the reinforcing portion extends along an entire periphery of the cover portion.