Upper cap group of square Li ion secondary battery

The utility model relates to a packaging tank of a square lithium secondary battery, in particular to the structure of the top head group used by the packaging tank. The top head group of the square lithium secondary battery comprises an upper cover which is suitable for fitting with the opening of a battery tank shell and provided with a shot hole; an anode terminal which is provided with a cylindrical particle with an expansion head at one end, wherein, the size of the cross section of the cylindrical particle is smaller than the shot hole of the upper cover while the expansion head is bigger than the shot hole; and an insulated gas sealing pad which is injection molding along the anode terminal to prevent the upper cover and the anode terminal touch each other and to fix the cylindrical particle in the shot hole of the upper cover. The expansion head of the cylindrical particle is arranged on the inner side of the upper cover while the other end of the cylindrical particle extends out of the lateral side of the upper plate.