(541d) 3D Porous Graphene Nanostructure Fabricated with a Simple, Fast, Scalable Process for Applications in 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 ^oC 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 m²/g was obtained through common carbonization and activation treatments. No time-consuming hydrothermal or sol-gel chemistries and no energy-demanding supercritical fluid or freeze drying operations are needed to form the 3D graphene monoliths. The starch/RGO material was applied 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 at the power density of 0.5 kW/kg and exhibiting an excellent high rate capability of a high power density of 9.9 kW/kg at the energy density of 9.6 Wh/kg, among the highest for carbon material based, gel-type, symmetric supercapacitors. These excellent capacitive performances may be attributed to the advantageous structural features of the starch/RGO material, including the large surfaces exposed to the electrolyte ions for capacitance generation, highly porous structure for fast mass transfer of the electrolyte ions, and three-dimensionally well-connected conductive paths for the involved charge transport. 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^o. It was also found that the starch/RGO based supercapacitor exhibited optimal performances in both energy and power densities at 80 ^oC and is thus applicable in a wide temperature range environment.