Assembly of graphene aerogels into the 3D biomass-derived carbon frameworks on conductive substrates for flexible supercapacitors

The biomass-derived carbon materials as ideal low-cost raw materials have recently presented great application potential in energy storage. However, the amorphous active carbon from biomass is usually required to be further processed into electrodes with binders and conductive agents due to their essentially poor electrical conductance, which limits the fabrication as free-standing electrodes for flexible supercpacitors. Here, we present a simple universal strategy toward assembling of graphene aerogels into the three-dimensional N-doping cotton-derived carbon frameworks, utilizing spontaneous reduction and assembly of graphene oxide on the Cu surface. Benefiting from the structural features, the free-standing N-doping cotton-derived carbon frameworks/graphene aerogels of hierarchical 3D interconnected structures exhibit considerably enhanced charge transport ability and energy storage capability (approaching 305, 225 and 170 F g⁻¹ at current densities of 0.1, 1 and 10 A g⁻¹, respectively). Moreover, the binder-free all-solid-state devices are also fabricated, and three flexible supercapacitors electrically connected in series could light up a LED light even under bent, which demonstrates excellent mechanical flexibility.