Ultrathin Nanosheet Assemblies of Three-Dimensional Spongy Carbon/Nitrogen-Doped Vanadium Nitride Cathode for High-Performance Aqueous Zinc-Ion Batteries

Abstract

Transition metal nitrides are considered promising electrode materials for energy storage due to their high theoretical capacity and chemical properties. However, their performance during electrode cycling still needs further improvement. Herein, we prepare C/N-doped VNNC-9 materials by a simple one-step high-temperature calcination strategy, presenting a three-dimensional (3D) spongy structure assembled from ultrathin nanosheets of 1.5 nm thickness, which introduces abundant Zn 2+ storage sites to exhibit multifaceted Zn 2+ storage capacity. Compared with bulky structures of VNNC materials, the 3D spongy structure of the VNNC-9 material exhibits an ultrahigh capacity and high cycle life; it displays 638.9 mAh•g −1 reversible capacity at 0.1 A•g −1 current density and 616.5 mAh•g −1 discharge capacity at 1 A•g −1 after 120 cycles with 96.7% capacity retention. Furthermore, the VNNC-9 electrode exhibits 116.9 mAh•g −1 capacity after 20,000 cycles at 10 A•g −1 with nearly 100% Coulombic efficiency. Meanwhile, it achieves 541.9 W h Kg −1 energy density at 102.6 W Kg −1 power density. Besides, a series of ex situ characterizations are performed for a detailed analysis of the mixed zinc storage mechanism, the transformation into an amorphous phase, and Zn 2+ intercalation/deintercalation. In summary, this report provides a new opportunity to fabricate high-performance and environmentally friendly aqueous zinc-ion batteries.

Unlatching the Additional Zinc Storage Ability of Vanadium Nitride Nanocrystallites

“…Lastly, due to the robust interaction between Zn 2+ and the VN lattice during the conversion of chemical energy to electrical energy, there is a periodic expansion/contraction of the lattice spacing, inevitably giving rise to volume variation and structural degradation. [27] The general approaches to address these challenges include the incorporation of buffering agents, [28] carbon-encapsulated engineering, [29][30][31] structural control engineering, [19] or even constraining the current during the charge-discharge of vanadium-based compounds have been proposed. [32] Although these methods have shown a significant impact in enhancing the Zn 2+ storage activity, the improvement is still marginal because simultaneously fulfilling the abovementioned challenges requisites of high energy density, high power density, and rapid charge-discharge rates is still an open question.…”