Power storage device comprising an electricity storage element, a case with an opening, and a sealing member sealing the opening

A power storage device comprising:

• an electricity storage element;
• a case housing the electricity storage element, the case having an opening;
• and
• a sealing member sealing the opening, wherein:
• the sealing member includes an elastic member fit in the opening,
• the elastic member contains an elastic polymer, a hindered phenol compound, and a filler,
• the hindered phenol compound having a phenol skeleton includes a first hindered group and a second hindered group, the first hindered group being bonded to a first substitution site of the phenol skeleton, the second hindered group being bonded to a second substitution site of the phenol skeleton, each of the first substitution site and second substitution site being adjacent to a substitution site of the phenol skeleton to which a phenolic hydroxy group is bonded,
• the first hindered group and the second hindered group each include one or more tertiary carbon atoms,
• one of the one or more tertiary carbon atoms in the first hindered group is bonded to the first substitution site,
• one of the one or more tertiary carbon atoms in the second hindered group is bonded to the second substitution site,
• a reaction heat of phenol radical formation for the hindered phenol compound ranges from 76.8 kcal/mol to 82 kcal/mol, inclusive,
• a content ratio of the hindered phenol compound included in the elastic member ranges from 1.5 parts by mass to 6 parts by mass, inclusive, with respect to 100 parts by mass of the elastic polymer included in the elastic member,
• the filler includes kaolin and talc,
• a content ratio of the talc included in the elastic member ranges from 50 parts by mass to 120 parts by mass, inclusive, with respect to 100 parts by mass of the elastic polymer included in the elastic member, and
• a proportion of the kaolin in total of the kaolin and the talc included in the elastic member is less than or equal to 70 mass %.