Graphene aided gelation of MXene with oxidation protected surface for supercapacitor electrodes with excellent gravimetric performance

Gravimetric and volumetric capacitance are the two important matrices for any supercapacitor device, but only moderate achievement has been realized till date on the first figure-of-merit for MXene based electrodes. In this study, aided by a small quantity (5 wt%) of graphene, an interfacial layer-by-layer self-assembly of MXene has been employed to develop hydrogel based supercapacitor electrodes that display excellent gravimetric capacitance of 653.7 F g(-1) at 2 mV s(-1) in three electrode setup. Very high areal (1442 mF cm(-2) ) and volumetric capacitance (similar to 1522 F cm(-3)) were also achieved by simple tuning of respective conditions like gelation time and electrolyte protected mechanical compression. Considering the fact that MXene is prone to oxidation at elevated gelation temperatures, this purely ambient gelation protocol is established to protect its redox active titanium sites. MXene-graphene hybrid hydrogel structures consisting of network of 2D-sheets can allow full utilization of metallic surfaces and redox active sites on MXene basal plane, and thereby display outstanding performance metrics. These hybrid hydrogels also show excellent cyclic stability even with commercial scale mass loading which can pave the way to their application in practical devices. (C) 2020 Elsevier Ltd. All rights reserved.