Disclosed herein is a sheet-shaped safety kit that is attached to opposite major surfaces of an electrode assembly for secondary batteries. The safety kit includes a group of metal sheets electrically connected to a cathode terminal of the electrode assembly, another group of metal sheets electrically connected to a cathode terminal of the electrode assembly, and an insulation sheet disposed between the two metal sheet groups. The metal sheets of one of the metal sheet groups are interconnected with each other at lower ends of the metal sheets, the lower-end interconnection part interconnecting the lower ends of the metal sheets has a width less than that of the metal sheets, and lower-end corners of the interconnected metal sheets are larger than lower-end corners of the metal sheets that are not interconnected with each other.