SC-CO₂-assisted process for a high energy density aerogel supercapacitor: the effect of GO loading

Energy density, safety, and simple and environmentally friendly preparation methods are very significant aspects in the realization of a compact supercapacitor. Herein we report the use of a supercritical CO₂-assisted gel drying process (SC-CO₂) for the preparation of porous electrodes containing dispersed graphene in a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) binder membrane to sandwich in a new portable supercapacitor based on graphene oxide (GO). A GO loading of 60 wt.% was found to give the best combination of factors (porosity, wettability, mechanical and electrochemical properties). Cycling voltammetry and charge/discharge studies showed an excellent capacitance behaviour and stability in an ionic liquid electrolyte, suggesting SC-CO₂ processing as a promising platform to produce highly bulky and porous films for supercapacitors. The supercapacitor device delivers a very high energy density of 79.2 Wh kg^-1 at a power density of 0.23 KW kg^-1 (current density 0.5 A g^-1, specific capacitance 36.2 F g^-1) while that of steel remains at 50.3 Wh kg^-1 at a power density of 2.8 KW kg^-1 (current density 6 A g^-1, specific capacitance 23.5 F g^-1).