Flexible Graphene-Based Composite Films for Supercapacitors with Tunable Areal Capacitance

Flexible supercapacitors based on paper-like electrodes have attracted significant interest because of the increasing demands in the energy storage, and they are recently claimed to be minimized and portable for meeting practical applications. As promising binder-free electrode materials in the supercapacitors, graphene-based films have been developed for enhancing their performance in energy storage by insetting "spacers" in-between nanosheets to prevent inevitable aggregations. In this study, a facile and versatile strategy is presented for fabricating graphene-based composite films by introducing activated carbonized cotton fibers to regulate the chemical composition, surface area and pore size distribution. The obtained composite films permit to present substantially increased energy storage capability (capacitance of 310 F g (1) and 150 F g 1 at 0.1 A g(1) and 10 A g (1) in 6 mol L-1 KOH electrolyte, respectively). Furthermore, tunable areal capacitance is realized by altering the stacked film layers without loss of mass specific capacitance. The devices based on composite films with excellent power density (up to 156.5 mW cm (2)) and energy density (240 mWh cm (2)) highlight a controllable, mini-sized and highefficiency stage for energy storage. Such unique strategy suggests great potential in the commercialization of portable electronic devices, which require greater capacitance in a limited area. (C) 2017 Elsevier Ltd. All rights reserved.