Fe-doping enabled a stable vanadium oxide cathode with rapid Zn diffusion channel for aqueous zinc-ion batteries

Abstract

Vanadium-based oxides with high theoretical specific capacity and open crystal structure are promising cathodes for aqueous zinc ion batteries. However, the frustrating dissolution and structural collapse of vanadium-based oxides, especially when cycling at a low current density, lead to severe performance degradation. Here, we demonstrate doping of Fe opens up a rapid Zn2+ diffusion channel, and results in a stable layer-structured vanadium oxide nanobelt (FeVO) with an expanded interlayer spacing up to 10.8 Å. This enables a cathode with high structural stability, leading to an outstanding cyclic stability of 300 cycles at a low current density of 0.5 A g−1 with a high retention of 94.6%. Even cycling at 0.2 A g−1, the Fe-doped vanadium oxide still maintains a retention of 93.6% after 150 cycles. A reversible co-intercalation mechanism of Zn2+ and H2O is further revealed via ex-situ X-ray powder diffraction (XRD) and X-ray photoelectron spectra techniques. Such boosted electrochemical performance is attributed to the large interlayer space providing ion diffusion path and a stable layered structure. These excellent characteristics of the prepared vanadium oxide cathode show great potential for high-performance aqueous zinc ion batteries.