▎ 摘　　要

NOVELTY - Energy storage device comprises: (a) two electrodes, where at least one electrode comprises a reduced graphene oxide film comprising a three-dimensional (3D) hierarchy of pores having a pore size of less than 1000 nm, and the film has a density of at least 0.1 g/cm3; (b) an electrolyte (503); and (c) an separator (504) disposed between the first electrode (502) and the second electrode (505). USE - The energy storage device is useful in super capacitors. ADVANTAGE - The energy storage device provides simple, yet versatile technique for the fabrication of super capacitors through the direct preparation of three dimensional porous reduced graphene oxide films by filtration and freeze casting and which exhibit improved performance. DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of symmetric two-electrode supercapacitor. First current collector (501) First electrode (502) Electrolyte (503) Separator (504) Second electrode (505)