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

Abstract

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 VO_x/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 VO_x/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 VO_x/NC porous-sphere electrode is ascribed to its distinctive architecture. The VO_x/NC porous spheres possess amorphous VO_x 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, VO_x/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 VO_x/carbon composites with high valence states (V⁵⁺ and V⁴⁺).