Electrochemical performance of Zn2VO4/ZnO nanocomposite material derived from Zn-V layered double hydroxides as a cathode for aqueous zinc ion battery

Aqueous zinc ion batteries (AZIBs) with Zn metal as an anode have become one of the ideal choices for grid-scale energy storage presenting the advantages of high safety, low cost, and high theoretical capacity. However, their practical applications are limited by slow electrode reaction kinetics and poor cycling performance. Herein, we successfully prepare Zn2VO4/ZnO nanocomposite materials with graded porous nanosheet morphology by calcining Zn-V layered double hydroxides (Zn-V-LDH) in Ar/H2 mixed gas. Further, the Zn2VO4/ZnO cathode for AZIBs exhibits 232.4 mA h g-1 capacity after 50 cycles at 0.1 A g-1 with 103.8% capacity retention, and could still reach 104.2 mA h g-1 capacity after 8000 cycles at 10 A g-1 with about 100% coulomb efficiency, which excellent electrochemical performance is attributed to the charge redistribution caused by the two-phase interface and the hierarchical porous nano-structures provide abundant reversible Zn2+ storage sites. A series of ex-situ characterizations reveal that Zn2VO4/ZnO electrode undergoes a phase transition to amorphous Zn2VO4/ZnO, which then follows by a classic zinc ion de/intercalation mechanism. In general, the construction of porous nanomaterials with a two-phase synergistic structure could be a major direction for the exploration of cathode materials, which will contribute to the development of high-performance AZIBs.