Free-standing hybrid films based on graphene and porous carbon particles for flexible supercapacitors
Free-standing flexible solid-state supercapacitors are attracting attention as a power supply for electronic equipment. Here we report a novel strategy to fabricate free-standing flexible hybrid papers made up of porous carbon particles combined with graphene sheets. The synergetic effect between the carbon particles and the graphene sheets entails two important advantages: (a) binder-free electrodes formed by carbon particles can be built with the assistance of the graphene sheets and (b) the restacking of the graphene sheets is avoided to a great extent due to the fact that the carbon particles act as spacers. These hybrid papers combine important properties for their use in solid-state supercapacitors: (a) large specific surface area, (b) good electrical conductivity, (c) high packing density and (d) excellent flexibility. They exhibit a volumetric electrochemical performance which is clearly superior to electrodes fabricated with carbon particles agglomerated with a binder. In addition, they achieve an excellent areal capacitance (103 mF cm−2) at current densities as high as 1400 mA cm−2 and are able to deliver a large amount of energy (∼12 μW h cm−2) at high power densities (316 mW cm−2). In this work, a robust, flexible and high-performance solid-state supercapacitor has been assembled using such hybrid papers.