Safety valve for gastight battery and gastight battery using safety valve

A safety valve for a gastight battery in which a thin-wall valve element is formed on a sealing plate which seals an opening portion of a battery case, and the valve element is opened when a battery internal pressure becomes a predetermined pressure or more so as to release a gas in the battery to the outside of the battery, the safety valve comprising:

• an outer annular groove formed of an annular thin wall which is formed on the periphery of the valve element and is provided for peeling off the whole valve element;
• an inner annular groove formed of an annular thin wall which is arranged in an area inside the outer annular groove;
• and
• a connecting groove formed of a straight thin wall which connects the outer annular groove and the inner annular groove, wherein
• the outer annular groove, the inner annular groove and the connecting groove are formed on the same side of the sealing plate which is an upper side of sealing plate arranged forming an outer side of the battery, a lower side of the sealing plate forming an inner side of the battery or the upper side and the lower side of the sealing plate, and
• a wall thickness of the inner annular groove and a wall thickness of the connecting groove are set larger than a wall thickness of the outer annular groove.