Rational design of hybrid Co3O4/graphene films: Free-standing flexible electrodes for high performance supercapacitors

Abstract

Flexible electrodes with superior mechanical and electrochemical properties are essential for flexible and foldable supercapacitors (SCs) for subminiature and integrated energy storage devices. Herein, we developed a novel and scalable method to fabricate highly flexible free-standing Co3O4/graphene film (GF) as robust supercapacitor electrode, in which nanostructured Co3O4 arrays directly grow on highly flexible GF substrates. Originating from the high mass loading of the Co3O4 as well as the synergistic effects of electrochemical active Co3O4 and conductive GF, the fabricated Co3O4/GF electrodes deliver outstanding electrochemical properties without current collectors or binders. The Co3O4 phase in the Co3O4/GF delivers a high capacitance contribution of 652 F g−1 after 3000 cycles at a current density of 2 A g−1, four times higher than the pristine Co3O4. More importantly, a superior rate capability of 665 F g−1 was achieved at a high current density of 20 A g−1. These results demonstrate that the flexible hybrid film electrodes possess significant potential for the application of wearable energy storage devices.