Synthesis of Nb2C MXene-based 2D layered structure electrode material for high-performance battery-type supercapacitors

The supercapacitor is a kind of electrochemical energy storage element, has attracted widespread attention, however, it is limited by a lack of ideal electrode materials with excellent cycle stability and high specific capacitance. To address this issue, we prepared Nb2CTx MXene-framework coated with Co3O4 to construct a robust 2D cross-linked structure. In this design, the self-assembly of Co3O4 between Nb2C MXene layers can effectively prevent the self-stacking of MXene sheets. The high conductivity and abundant active groups on the surface of MXenes provide a large number of active sites for the uniform distribution of Co3O4 on Nb2C MXene. The Co-MXene electrode achieves a specific capacitance of up to 1061 F g−1 at the current density of 2 A g−1, which is higher than the pure Co3O4 electrode and Nb2C MXene electrode. The asymmetric supercapacitors (ASCs) of Co-MXene//AC delivers specific energy densities (Es) of 60.3, 42.5, 31.0, 19.7 Wh kg−1 at specific power density (Ps) of 0.67, 2.0, 3.4, and 6.8 kW kg−1, respectively. The capacitance retention rate of 93% after 1000 cycles at 5 A g−1. The study provides a valuable guideline for fabricating satisfactory electrochemical energy storage devices by a feasible method.