High-Mass-Loading vanadium nitride /N-Doped rGO cathode for fast and stable Zinc-Ion storage

Vanadium nitride (VN) has sparked much interest because of the abundant reserves, multivalent states, and high theoretical specific capacity in aqueous zinc-ion batteries (AZIBs). However, the direct utilization of VN in AZIBs is still huge challenges including sluggish kinetics, low-mass-loading and suboptimal cycling stability. Herein, an exquisite method is employed to enhance the electrochemical performance via compositing of VN with nitrogen-doped reduced graphene oxide (VN/N-rGO) and 3D printing technique. The designed conductive network and hierarchical porous structure enhance the reaction kinetics of the electrode and inhibit its dissolution, thereby improving cycling stability. The fabricated electrodes demonstrate superior reversible capacity of 529.8mAh g⁻¹, excellent long-cycle stability (261.6mAh g⁻¹ after 1000 cycles at 8.0 A g⁻¹) and good rate capability. Furthermore, the high-mass-loading VN/N-rGO electrodes (∼13 mg cm⁻²) are constructed through material extrusion 3D printing, and the electrodes still display a high reversible capacity of 390.2mAh g⁻¹. The electrochemical reaction mechanism of VN with Zn ions has been extensively studied, indicating that VN irreversibly transforms into Zn₃(OH)₂V₂O₇(H₂O)₂ during first cycle, and Zn ions reversibly insert into/extract from the interlayer of Zn₃(OH)₂V₂O₇(H₂O)₂ during the following cycles. This work demonstrates that VN holds significant potential as high-mass-loading cathode in AZIBs.