High-capacity zinc vanadium oxides with long-term cyclability enabled by in-situ electrochemical oxidation as zinc-ion battery cathode

Abstract

The rechargeable aqueous zinc ion batteries hold great promise owing to their non-flammability and low cost, but are extremely limited by the lack of suitable cathode materials. Vanadium oxides such as V2O5·nH2O, Zn0.25V2O5·nH2O, Ca0.24V2O5·0.83H2O, and so on have been exploited owing to their high Zn2+ storage activity. However, due to the structural disintegration because of the impact of Zn2+ transportation and poor conductivity, their low capacity, poor cyclability and rate property hinder further utilization. Herein, we report the stable zinc vanadium oxides Zn0.36V2O5·nH2O as cathode material for zinc-ion batteries. The zinc vanadium oxides with different stoichiometry converted from in-situ electrochemical oxidation of VOOH precursors in various space groups. The introduction of zinc atoms improves the conductivity of the materials and stabilizes the host structure by bonding with the host oxygen atoms without hindering the interlayer migration of mobile Zn2+, thus greatly optimizing the comprehensive behaviors of the batteries. Ex-situ XRD spectra collected at various states show no shift during (dis)charging and the electrode morphology under different cycles remains intact, indicating the high reversibility and stability. The as-prepared Zn0.36V2O5·nH2O presents a high specific capacity of 508.3 mAh g−1 and 343 mAh g−1 at current densities of 0.5 A g−1 and 5.0 A g−1, and excellent capacity retention of 95% and 80% after 2000 and 5000 cycles respectively. The role of interlayer intercalated-Zn on the stability of vanadium oxides is revealed via density functional theory simulations. In addition, materials with low crystallinity provide shortcuts for ion transportation. The in-situ conversion mechanism of zinc vanadium oxides and the later dual ion energy storage mechanism of which are illustrated in detail.