Scalable Fabrication of Photochemically Reduced Graphene-Based Monolithic Micro-Supercapacitors with Superior Energy...

Micro-supercapacitors (MSCs) hold great promise as highly competitive miniaturized power sources satisfying the increased demand of smart integrated electronics. However, single-step scalable fabrication of MSCs with both high energy and power densities is still challenging. Here we demonstrate the scalable fabrication of graphene-based monolithic MSCs with diverse planar geometries and capable of superior integration by photochemical reduction of graphene oxide/TiO₂ nanoparticle hybrid films. The resulting MSCs exhibit high volumetric capacitance of 233.0 F cm^-3, exceptional flexibility, and remarkable capacity of modular serial and parallel integration in aqueous gel electrolyte. Furthermore, by precisely engineering the interface of electrode with electrolyte, these monolithic MSCs can operate well in a hydrophobic electrolyte of ionic liquid (3.0 V) at a high scan rate of 200 V s^-1, two orders of magnitude higher than those of conventional supercapacitors. More notably, the MSCs show landmark volumetric power density of 312 W cm^-3 and energy density of 7.7 mWh cm^-3, both of which are among the highest values attained for carbon-based MSCs. Therefore, such monolithic MSC devices based on photochemically reduced, compact graphene films possess enormous potential for numerous miniaturized, flexible electronic applications.