Multilayer-Folded Graphene Ribbon Film with Ultrahigh Areal Capacitance and High Rate Performance for Compressible Supercapacitors

Limited by 2D geometric morphology and low bulk packing density, developing graphene-based flexible/compressible supercapacitors with high specific capacitances (gravimetric/volumetric/areal), especially at high rates, is an outstanding challenge. Here, a strategy for the synthesis of free-standing graphene ribbon films (GRFs) for high-performance flexible and compressible supercapacitors through blade-coating of interconnected graphene oxide ribbons and a subsequent thermal treatment process is reported. With an ultrahigh mass loading of 21 mg cm⁻², large ion-accessible surface area, efficient electron and ion transport pathways as well as high packing density, the compressed multilayer-folded GRF films (F-GRF) exhibit ultrahigh areal capacitance of 6.7 F cm⁻² at 5 mA cm⁻², high gravimetric/volumetric capacitances (318 F g⁻¹, 293 F cm⁻³), and high rate performance (3.9 F cm⁻² at 105 mA cm⁻²), as well as excellent cycling stability (109% of capacitance retention after 40 000 cycles). Furthermore, the assembled F-GRF symmetric supercapacitor with compressible and flexible characteristics, can deliver an ultrahigh areal energy density of 0.52 mWh cm⁻² in aqueous electrolyte, almost two times higher than the values obtained from symmetric supercapacitors with comparable dimensions.