Engineering VO structure by integrating oxygen vacancies for improved zinc-ion storage based on cation-doping regulation with electric density.

Aqueous zinc-ion batteries (ZIBs) have attracted enormous attention for future energy-storage devices owing to their high theoretical capacity and environmental friendliness. However, obtaining cathodes with a high specific capacity and fast reaction kinetics remains a huge challenge. Herein, Cu-VO material with a thin sheet microsphere structure composed of nanoparticles was prepared by a simple hydrothermal reaction, which improved reaction kinetics and specific capacity. Pre-embedding Cu into VO to introduce abundant oxygen vacancies extended the interlayer distance to 1.16 nm, weakened the effect of the V-O bonds, and improved the electrical conductivity and structural stability. At the same time, the influence of different valence metal ions (M = K, Cu, Fe, Sn, Nb, and W) pre-embedded in VO was studied. Benefiting from a large interlayer spacing, high electrical conductivity, and excellent structural stability, the Cu-VO electrode demonstrated a high specific capacity of 455.9 mA h g at 0.1 A g. Importantly, when the current density was increased to 6 A g, the Cu-VO electrode still achieved a high specific capacity of 178.8 mA h g and maintained a high capacity retention of 76.5% over 2000 cycles.