Sealing gasket and tubular battery incorporating sealing gasket

A sealing gasket for a tubular battery, the sealing gasket comprising:

• a disc-shaped partition portion;
• an outer peripheral portion provided to stand from a peripheral edge of the partition portion and held between an open end of a metal battery can and a dish-shaped metal sealing plate;
• and
• a plurality of stress buffer portions formed of annular grooves formed concentrically in the partition portion,
• the tubular battery including
• the metal battery can having a bottomed tubular shape and has the open end subjected to inward diameter reduction,
• a power generation element housed in the battery can,
• the dish-shaped metal sealing plate fitted and attached to the open end subjected to the inward diameter reduction, and
• the sealing gasket, made of resin and held between the open end and the sealing plate,
• wherein Ha/H, a ratio of a thickness Ha of a region of the partition portion in which the plurality of stress buffer portions are formed to an overall height H from a lowest position to a highest position of the sealing gasket, is 15% or more and 30% or less.