Adjusting the V5+ content of vanadium oxide cathodes for high-performance Zn-ion batteries by aging

Vanadium oxides are promising cathode materials with great potential. Here, we present a simple, safe, and environmentally friendly aging treatment to change the content of V5+ in vanadium oxides. The influence of different V5+ contents in vanadium oxides cathodes on the properties of Zn-ion batteries (ZIBs) is studied. V6O13 and V3O7/V6O13 nanosheets are synthesized by aging VO2 precursors for different periods of time. V6O13 is found to exhibit higher specific capacity and excellent cycling performance compared to VO2 and V3O7/V6O13. It is also characterized by an extremely high capacity of 300 mA h g−1 at a high current density of 5 A g−1. At 0.3 A g−1, it maintains a capacity of 421 mA h g−1 during 100 cycles with a high capacity retention rate of 95%. Changes in the vanadium valence state, structure, and morphology of electrodes during charging and discharging are also investigated for a better understanding of the underlying electrochemical processes.