Energy Storage Mechanism of Vanadium Nitride via Intercalating Different Atomic Radius for Expanding Interplanar Spacing

Abstract

As a promising anode material in supercapacitors, vanadium nitride has been widely concerned due to its ultra-high theoretical specific capacitance. However, its routine test capacitance value is still far from the theoretical value and its energy storage mechanism is controversial. In order to solve these two key problems, here we prepare interplanar spacing expanded vanadium nitride materials with different impurity atoms intercalation from two anionic precursors of vanadium-based metal organic frameworks with different functional groups. The obtained vanadium nitride reaches a higher specific capacitance; and further, through ex situ X-Ray diffraction and in situ Raman, the charge storage of vanadium nitride is contributed by two processes: the first benefit is from the K+ de/intercalation in the interplanar spacing, and the other one is derived from the redox reaction with OH− by adsorption on surface. Furthermore, both of the first principle calculation and extended experiments support this idea. We believe that such detailed research on the energy storage mechanism can provide a clear idea for the application of metal nitrides in supercapacitors and other energy storage devices.