Abstract: Power supply device includes: battery stack in which a plurality of battery cells each having electrode terminal formed on a top surface thereof are stacked; a pair of end plates respectively covering end surfaces in a stacking direction of battery stack; fastening member that fastens the pair of end plates to each other; and insulating member interposed between a side surface of battery stack and fastening member. Insulating member has groove extending in a stacking direction of battery stack on a surface facing battery stack.

Abstract: A power supply device includes: a battery stack formed by stacking a plurality of battery cells; a separator disposed between the battery cells; and a fixing member for fastening the battery stack in a stacking direction. The separator includes an outer peripheral frame and a heat insulating base material member provided in an opening of the outer peripheral frame. The outer peripheral frame is disposed on an outer periphery of a stacking surface of the battery cell and has an opening inside, and the heat insulating base material member has flexibility of being deformed by being pressed by expanding of the stacking surface of the battery cell. The outer peripheral frame has higher rigidity than the heat insulating base material member, and specifies an interval between the adjacently stacked battery cells. The flexible heat insulating base material member absorbs expansion of the stacking surface of the battery cell.