Hierarchical V4C3TX@NiO-reduced graphene oxide heterostructure hydrogel and defective reduced graphene oxide hydrogel as free-standing anode and cathode for high-performance asymmetric supercapacitor

Abstract

Abstract Asymmetric supercapacitors (ASCs) based on a battery-type anode and a capacitive-type cathode have been attracting extensive interest because of their high energy density. Herein, NiO nanosheets are hydrothermally deposited onto a V4C3TX substrate, which are then assembled into a 3D porous heterostructure hydrogel through a graphene oxide-assisted self-convergence hydrothermal process at low temperatures. The resultant hierarchical V4C3TX@NiO-reduced graphene oxide (RGO) hydrogel exhibits an ultrahigh specific capacitance up to 1014.5 F g− 1 at 1 A g− 1. Separately, a defective reduced graphene oxide (DRGO) hydrogel is prepared by a cost-effective hydrothermal procedure followed by cobalt-catalyzed gasification, which shows a higher specific capacitance (258 F g− 1 at 1 A g− 1) than untreated RGO hydrogel (176 F g− 1). These two electrodes are then assembled into an ASC, the device features a stable operating voltage of 1.8 V, a maximum energy density of 86.22 Wh kg− 1 at 900 W kg− 1, along with good cycling stability at 96.4% capacitance retention after 10,000 cycles at 10 A g− 1. This work highlights the unique potential of MXenes-based materials for the construction of high-performance ASCs.