Patent attributes
One aspect of the present invention is an energy storage device including: 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, a surface pressure acting on the outer case in the direction of stack is 1 k Pa or more, the nonaqueous solvent contains a fluorinated cyclic carbonate, and the nonaqueous electrolyte has an electric conductivity at 25° C. of 0.75 S/m or more.
