Facile preparation of urchin-like morphology VO-VN nano-heterojunction cathodes for high-performance Aqueous zinc ion battery.

Rechargeable aqueous zinc ion batteries (RAZIBs) are of interest for energy storage in smart grids. However, slow Zn diffusion kinetics, insufficient active sites, and poor intrinsic conductivity are always challenging to exploit the huge potential of the batteries. Here, we prepare VO-VN nano-heterojunction composites with sea urchin-like morphology as the cathode for AZIBs. The electrode achieves high capacities (e.g., 0.1 A g, 532.6 mAh g), good rate and cycle performance (263.4 mAh g at 5 A g current density with 90.8% capacity retention). Detailed structural analyses suggest that the VO-VN composite is composed of different crystal planes of VO and VN, which form an efficient heterogeneous interfacial network in the bulk electrode, accounting for its good electrochemical properties. Theoretical calculations reveal that compared with VO, VN and physically mixed VO/VN, the VO-VN heterostructure exhibits good cation adsorption and electrode conductivity, thereby accelerating the charge carrier mobility and electrochemical activity of the electrode. Moreover, ex-situ characterization techniques are utilized to investigate the zinc storage mechanism in detail, providing new ideas for the development of AZIBs cathode materials through the construction of heterojunction structures.