Separator for insulating adjacent battery cells and power supply device

A power supply device comprising:

• a plurality of battery cells having a flat right-angled parallelepiped shape;
• and
• a plurality of separators each insulating a corresponding pair of adjacent battery cells among the plurality of battery cells, wherein
• each of the plurality of separators includes:
• a heat insulating sheet arranged between the adjacent battery cells;
• and
• an insulating molded member holding the heat insulating sheet, the insulating molded member includes:
• a lower wall covering lower surface of each of the adjacent battery cells;
• and
• a holder holding the heat insulating sheet with a gap disposed between the heat insulating sheet and the lower wall,
• the heat insulating sheet includes at least one through hole or bottomed hole,
• the holder is a protrusion insertably disposed in the at least one through hole or the bottomed hole, and
• the insulating molded member further includes an upper wall partially covering upper surfaces of an adjacent cell adjacent to the one of the plurality of battery cells among the plurality of battery cells, and the holder is included in the upper wall.