Aluminium-doped vanadium nitride as cathode material for high-performance aqueous zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) are increasingly favored for their environmentally friendly and impressive energy storage performance. Vanadium nitride (VN) is receiving much attention as a cathode material for AZIBs due to its high electrical conductivity and controllable structure. However, the direct use of VN in AZIBs presents challenges such as sluggish kinetics, insufficient specific capacity and limited stability. Herein, a heteroatom doping strategy is utilized to improve the electrochemical energy storage performance of the VN by incorporating aluminium (Al) via a hydrothermal process and a subsequent calcination treatment. Electrochemical characterizations indicate that the as-synthesized aluminium-doped VN (Al-doped VN) exhibits an outstanding specific capacity of 544 mAh·g−1 at 1 A g−1 and retains a high rate capacity of 275.6 mAh·g−1 at 10 A g−1. Further studies show that the Al incorporation effectively modulates the electronic configuration of the VN, which accelerates the charge transfer kinetics and thus enhances the electrochemical storage performance of VN. The phase transformation mechanism of the Al-doped VN is also investigated and the results show that the VN undergoes partial conversion into Zn3(OH)2V2O7·2H2O during the charge/discharge process. An aluminium doping strategy is proposed to modulate the electronic structure of vanadium nitride (VN) via a hydrothermal process and a subsequent calcination treatment, and the as-synthesized Al-doped VN exhibits enhanced electrochemical storage performance as a cathode material for aqueous zinc-ion batteries. [Display omitted] •Al is successful incorporated into vanadium nitride (VN) to form Al-doped VN cathode.•Al-VN exhibits a capacity of 544 mAh·g−1 at 1 A g−1 and satisfactory rate capacity.•Al doping modulates the electronic structure and expands the lattice spacing of VN.•Doping increases ion diffusion rate and conductivity, thus enhancing rate capacity.•Phase transformation mechanism of Al-doped VN during charge/discharge is elucidated.