Power storage device including power storage cells having a positive electrode, a negative electrode, a separator, and an accommodation chamber for a liquid electrolyte

A power storage device includes power storage cells that includes a positive electrode, a negative electrode, a separator, and an accommodation chamber accommodating a liquid electrolyte in a liquid-tight manner. The power storage device includes a cell stack in which the power storage cells are stacked in series. A side surface of the cell stack is covered with a seal portion made of a plastic. A terminal positive electrode current collector and a terminal negative electrode current collector located in the outermost layer of the cell stack are made of a high thermal conductivity material having a thermal conductivity greater than or equal to 100 W/(m·K). The power storage device includes a positive electrode cooling unit, which cools the terminal positive electrode current collector, and a negative electrode cooling unit, which cools the terminal negative electrode current collector. The liquid electrolyte contains an ester compound.