Electrochemically induced amorphous and porous VOx/N-doped carbon spheres as a cathode for advanced aqueous zinc-ion batteries

Vanadium-based oxides have captured considerable attention as ZIB cathodes benefiting from their rich valences and superior theoretical capacity. However, vanadium-based oxides still suffer from structural instability, low electronic conductivity, and slow reaction dynamics, which will lead to poor zinc ion storage performance. Herein, amorphous VOx/NC porous spheres were fabricated by in situ, electrochemically-induced vanadium-polydopamine-derived crystalline V2O3/NC porous spheres. As a zinc-ion battery cathode, the VOx/NC porous spheres exhibit a sustainable capacity of 233 mA h g−1 at 5 A g−1 upon 1500 cycles and superior rate property. The excellent electrochemical performance of the VOx/NC porous-sphere electrode is ascribed to its distinctive architecture. The VOx/NC porous spheres possess amorphous VOx with a higher oxidation states of V5+/V4+, which can increase the theoretical energy density, provide more active sites, and improve Zn2+ diffusion kinetics. Furthermore, VOx/NC porous spheres with a porous core–shell architecture can enhance electrical conductivity and ensure electrolyte accessibility. This synthesis strategy can be potentially extended to fabricate other VOx/carbon composites with high valence states (V5+ and V4+).