Direct synthesis of vanadium pentoxide powder with carbon recombination as aqueous zinc-ion battery cathode

Advanced energy storage technologies have been developed to achieve safe, high-capacity, and stable cathode materials for aqueous Zn-ion batteries. Vanadium oxide has lately become a popular cathode material thanks to its advantages of a sufficient operating voltage window and a highly reversible redox reaction. However, vanadium pentoxide has certain drawbacks, such as poor electrical conductivity and slow ion diffusion. To resolve these problems, V2O5 sheets with amorphous carbon were synthesized by an ultrafast (within one minute), lower temperature (180 celcius), one-step and large-scale combustion synthesis method. We demonstrate the introduction of carbon improves the conductivity and increases the content of low-valence vanadium, resulting in higher electrochemical activity and lower polarization of V2O5/C. Moreover, the introduction of C increases the concentration of oxygen defects in V2O5, further enhancing its conductivity and providing higher active sites for electrochemical reactions, thereby increasing its battery capacity. The synthesized V2O5/C sample exhibited a specific capacitance of 220 mAh g-1 (compared to 180 mAh g-1 for V2O5) in aqueous electrolytes at 4 A g-1, demonstrating a high specific capacity of 85.5% after 500 cycles with nearly 100% Coulomb efficiency. These results indicate improved specific capacitance and cyclic stability.