Flexible free-standing graphene paper with interconnected porous structure for energy storage

A novel porous graphene paper is prepared via freeze drying a wet graphene oxide gel, followed by thermal and chemical reduction. The macroscopic structure of the formed graphene paper can be tuned by the water content in the gel precursor. With 92% water content, an interconnected macroporous network can be formed. This porous graphene (PG) paper exhibits excellent electrochemical properties. It can deliver a high discharge capacity of 420 mA h g^-1 at a current density of 2000 mA g^-1 when used as binder-free lithium ion battery anode. PG paper exhibits a specific capacitance of 137 F g^-1 at 1 A g^-1 in a flexible all-solid-state supercapacitor with PVA/H₂SO₄ electrolyte. It can maintain 94% of its capacitance under bending. This electrochemical performance and mechanical flexibility makes it an excellent material for flexible energy storage devices.