A high-performance supercapacitor based on free-standing V4C3TX@NiO-reduced graphene oxide core–shell hierarchical heterostructured hydrogel electrodes

Abstract

Exploration of new MXene-based materials with excellent electrical conductivity and a high redox-active surface as high electrochemical performance supercapacitor electrodes is a very promising field. However, it remains challenging to have electrode materials that feature ultrahigh specific capacitance. In this work, NiO nanoflowers uniformly grow onto a V₄C₃T_X substrate to form a core–shell hierarchical V₄C₃T_X@NiO heterostructure, and then the heterostructure is incorporated into a 3D interconnected porous hydrogel via a hydrothermal graphene oxide (GO)-gelation method at low temperatures. Due to the synergistic effect among each components as well as the significant prevention of the aggregation of V₄C₃T_X, the free-standing V₄C₃T_X@NiO-reduced graphene oxide (RGO) heterostructured hydrogel electrodes exhibit an ultrahigh specific capacitance of up to 1009.5 F g⁻¹ at 1 A g⁻¹, in comparison to those of V₄C₃T_X@NiO (665.3 F g⁻¹) and V₄C₃T_X (184 F g⁻¹), excellent cycling stability (capacity retention rate is 97.4% for the device after 10 000 cycles at 10 A g⁻¹), and a maximum energy density of 61.13 W h kg⁻¹ at a power density of 526.32 W kg⁻¹. This work highlights the unique potential of V₄C₃T_X-based heterostructured hydrogels as inspired electrode materials for low-cost supercapacitor devices.