Energy storage device

An energy storage device comprising:

• an electrode assembly including a negative electrode and a positive electrode that are stacked on each other with a separator interposed therebetween;
• a nonaqueous electrolyte containing a nonaqueous solvent;
• and a flat outer case housing the electrode assembly and the nonaqueous electrolyte, wherein the electrode assembly is disposed in the outer case in a compressed state so that the electrode assembly is pressurized in a direction of stack,
• the energy storage device further comprises a pressing member that pressurizes the electrode assembly in the direction of stack,
• a surface pressure acting on the outer case in the direction of stack is 100 kPa or more, the nonaqueous solvent contains a fluorinated cyclic carbonate, the nonaqueous electrolyte has an electric conductivity at 250 C of 0.75 S/m or more and 0.95 S/m or less, and the nonaqueous solvent further contains a linear carbonate.