3D Porous Graphene Nanostructure from a Simple, Fast, Scalable Process for High Performance Flexible Gel-Type Supercapacitors

A simple, fast, and scalable mix-and-heat process was developed for production of three-dimensional (3D) porous graphene nanostructure. The process involves only mixing and heating of starch and a graphene oxide (GO) suspension at 90 °C for 10 min to form 3D graphene monoliths, from which a three-dimensionally well-connected porous graphene nanostructure, starch/RGO, possessing a high specific surface area of 1519 m 2 g –1 was obtained. The starch/RGO material was used as the electrode material to fabricate flexible, gel-type symmetric supercapacitors of outstanding capacitive performances, delivering a high energy density of 19.8 Wh kg –1 at the power density of 0.5 kW kg –1 and exhibiting an excellent high rate capability of a high power density of 9.9 kW kg –1 at the energy density of 9.6 Wh kg –1, among the highest for pristine carbon material based gel-type, symmetric supercapacitors. The cycling stability of the starch/RGO based supercapacitor was excellent, with a high specific capacitance retention rate of 80% after 8000 cycles at 10 A g –1 . The starch/RGO based supercapacitor exhibited outstanding mechanical stability with a retention rate of 90% in both energy and power densities at a large bending angle of 138° and functioned well in a wide temperature range environment.