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

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 Zn2+ storage sites to exhibit multifaceted Zn2+ 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 Zn2+ intercalation/deintercalation. In summary, this report provides a new opportunity to fabricate high-performance and environmentally friendly aqueous zinc-ion batteries.