Method for preparing three-dimensional graphene structure and energy storage device

An energy storage device comprising:

• a first electrode structure including a first current collector and a first graphene structure disposed on the first current collector, in which the first graphene structure has a first cavity therein, the first cavity having an average diameter of about 1 μm to 1 mm, and first nanopores extending through an outer surface and an inner surface of the first graphene structure to be connected with the first cavity;
• a second electrode structure spaced apart from the first electrode structure and including a second current collector and a second graphene structure disposed on the second current collector, wherein the second graphene structure has a second cavity therein, the second cavity having an average diameter of about 1 μm to 1 mm, and second nanopores extending through an outer surface and an inner surface of the second graphene structure to be connected with the second cavity;
• an electrolyte interposed between the first electrode structure and the second electrode structure;
• and
• a separation film in the electrolyte,
• wherein the electrolyte is provided in the first cavity, the first nanopores, the second cavity, and the second nanopores.