Energy storage device

An energy storage device (10) including a positive electrode (410), a negative electrode (420), a separator (430) disposed between the positive electrode (410) and the negative electrode (420), and a non-aqueous electrolyte, wherein the negative electrode (420) includes non-graphitizable carbon as a negative electrode active material, and the separator (430) has a thickness of 10 to 30 µm and an air permeability of 10 to 180 sec/100 cc.