A universal fabrication strategy for MOFs-driven vanadium-based composite for aqueous zinc ion batteries

The shortage of ideal cathode materials for aqueous zinc-ion batteries (AZIBs) hinders its further development of AZIBs due to metal ion dissolution and poor conductivity. Herein, the MOFs-driven vanadium-based composite as the cathode material is fabricated by simple hydrothermal method followed by annealing process. Typically, the vanadium source is added during the synthesis of MOFs and then it is calcined in an inert atmosphere to generate carbon-coated and metal ion pre-intercalated vanadium-based composites. Among them, the metal-ion is used as active sites and pre-intercalated in the vanadium oxide, which can alleviate the problem of structural collapse and improve the cycling stability. In addition, PVP is added as an assistance in the process of synthesizing MOFs, which can improve the dispersion of the material and restrain its agglomeration. Moreover, the surface of the vanadium oxide after calcination is also coated with nitrogen-doped carbon layer, which can adjust the electronic structure and surface properties of cathode materials, thereby enhancing the reaction kinetics and electrochemical performances. The Cu-MOF derived vanadium-based materials have abundant active sites and stable crystal structures, which can effectively alleviate the dissolution of vanadium-based materials. Because of the synergistic effects of Cu²⁺ pre-intercalated and nitrogen-doped carbon layers, CuVO electrode exhibits the excellent cycling stability with a higher discharge capacity of 158.6 mAh·g⁻¹, and the capacity retention is up to 95.6 % even at a large current density of 5.0 A·g⁻¹ after 4000 cycles. These intriguing designs will present a novel avenue for the construction of cathode with satisfactory electrochemical performance for AZIBs.