CNT-rGO Hydrogel-Integrated Fabric Composite Synthesized via an Interfacial Gelation Process for Wearable Supercapacitor Electrodes.

We demonstrate a flexible and stretchable supercapacitor assembled via straightforward interfacial gelation of reduced graphene oxide (rGO) with carbon nanotube (CNT) on a stretchable fabric surface. The difference between the redox potential of aqueous graphene oxide (GO) dispersion, prepared using a modified Hummers' method, and of a solid Zn plate, which was used as an external stimulus, induces a spontaneous reduction of GO flakes forming porous CNT-rGO hydrogel at the liquid-solid interface. With the aid of Zn, a macroporous and flexible CNT-rGO hydrogel was fabricated on a stretchable fabric platform using a facile fabrication method, and the CNT-rGO fabric composite was assembled into a supercapacitor to demonstrate its feasibility as a wearable electrode. The porous structure of the as-formed CNT-rGO fabric composite allows excellent electrolyte accessibility and ion transport that result in a fast charge/discharge rate up to 100 mV/s and a large areal capacity of 10.13 mF/cm at a discharge rate of 0.5 mA (0.1 mA/cm). The inclusion of one-dimensional CNT as conductive bridges allows an excellent capacity retention of 95.2% after complete folding of the electrode and a capacity retention of 93.3% after 1000 bending cycles. Additional stretching test displayed a high capacity retention of 90.0% even at an applied strain as high as 50%, overcoming previous limitations of brittle graphene-based electrodes. This low-cost, lightweight, easy to synthesize, stretchable supercapacitor holds promise for next-generation wearable electronics and energy storage applications.