Polydopamine supporting method fabricating vanadium nitride nanoparticle enclosed into hierarchical hollow carbon nanospheres for supercapacitors

Nanostructure is crucial for achieving electrode materials with high capacity and high-power ascribing to pleasing specific surface area, intrinsic safety, and satisfactory ion transport pathways; nevertheless, the structural collapse that occurs during high-temperature treatment may lead to a decrease in the specific surface area of the electrode material, causing technical obstacles, and hence affecting its practical applicability. Vanadium nitride has become a promising electrode material since its superior conductivity and desirable theoretical capacity; unfortunately, its practical application is hindered by its limited rate capability, cycle stability, and tendency to dissolve in alkaline solutions. In this study, a template-free method is employed to prepare hollow nanosphere structures through the self-supporting effect of dopamine. When subjected to high-temperatures, it can successfully hinder the collapse of the hollow nanostructures. Graded vanadium nitride nanoparticles are generated in this process and encapsulated in hollow nanostructures. The issues of vanadium nitride dissolution and low transport rate in alkaline electrolytes can be efficiently resolved by leveraging the self-supporting action of dopamine and the subsequent formation of hierarchical vanadium nitride nanoparticles. The anode material endows a capacity of 387.14 F g−1 at a current density of 0.5 A g−1, as well as a coulombic efficiency of 98.28 % even after 10, 000 cycles at a current density of 3 A g−1. Additionally，the assembled device can achieve a maximum power density of 4, 000 W kg−1 and an energy density of 22.89 Wh Kg−1. This anode material displays potential applications in energy storage devices and offers a novel approach to material preparation.