A rechargeable battery comprising: an electric cell comprising a casing, a positive electrode, and a negative electrode; an upper connection cap electrically connected to the positive electrode and made of an electrically conductive material, wherein the upper connection cap further comprises a first base section which is fixed to the positive electrode and comprises a center hole, and a first support section which protrudes from the first base section and comprises a top portion, a side portion, and a center hole; a lower connection cap electrically connected to the negative electrode and made of an electrically conductive material, wherein the lower connection cap further comprises a second base section which is fixed to the negative electrode and comprises a center hole, and a second support section which protrudes from the second base section and comprises a top portion, a side portion, and a center hole; and a female member of a first mechanical fastener and a male member of a second mechanical fastener, wherein one of the female member of the first mechanical fastener and the male member of the second mechanical fastener is connected to the upper connecting cap and the other of the female member of the first mechanical fastener and the male member of the second mechanical fastener is connected to the lower connecting cap, wherein the female member is a nut comprising a head, a threaded hole; and a locking portion extended from the head, and the male member is a bolt comprising a head a locking portion extended from the head and a threaded pole characterized in that the nut is clinched to the first support section, wherein the locking portion of the nut is clinched to the center hole of the first support section, and wherein the nut comprises a first protrusion combined with a surface of the head; a second protrusion combined with a surface of the first protrusion; and a third protrusion combined with a surface of the second protrusion, the second protrusion having a diameter smaller than those of the first and third protrusions (151, 153) to provide a receive portion between the first and third protrusions (151, 153), the receive portion being filled with a material of the upper connection cap and the bolt is clinched to the center hole of the second support section, wherein the locking portion of the bolt is clinched to the second support section. an electric cell comprising a casing, a positive electrode, and a negative electrode; an upper connection cap electrically connected to the positive electrode and made of an electrically conductive material, wherein the upper connection cap further comprises a first base section which is fixed to the positive electrode and comprises a center hole, and a first support section which protrudes from the first base section and comprises a top portion, a side portion, and a center hole; a lower connection cap electrically connected to the negative electrode and made of an electrically conductive material, wherein the lower connection cap further comprises a second base section which is fixed to the negative electrode and comprises a center hole, and a second support section which protrudes from the second base section and comprises a top portion, a side portion, and a center hole; and a female member of a first mechanical fastener and a male member of a second mechanical fastener, wherein one of the female member of the first mechanical fastener and the male member of the second mechanical fastener is connected to the upper connecting cap and the other of the female member of the first mechanical fastener and the male member of the second mechanical fastener is connected to the lower connecting cap, wherein the female member is a nut comprising a head, a threaded hole; and a locking portion extended from the head, and the male member is a bolt comprising a head a locking portion extended from the head and a threaded pole characterized in that the nut is clinched to the first support section, wherein the locking portion of the nut is clinched to the center hole of the first support section, and wherein the nut comprises a first protrusion combined with a surface of the head; a second protrusion combined with a surface of the first protrusion; and a third protrusion combined with a surface of the second protrusion, the second protrusion having a diameter smaller than those of the first and third protrusions (151, 153) to provide a receive portion between the first and third protrusions (151, 153), the receive portion being filled with a material of the upper connection cap and the bolt is clinched to the center hole of the second support section, wherein the locking portion of the bolt is clinched to the second support section.