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

Zn 0.36 V 2 O 5 ·nH 2 O is converted from VOOH through an in-situ electrochemical oxidation process. When used as ZIBs cathode, it stores energy by Zn 2+ /H + dual ions and delivers a high specific capacity (508.3 mAh g −1 at 0.5 A g −1 ), a long-term cyclability (80% at 5 A g −1 after 5000 cycles) and brilliant rate performance (348.6 mAh g −1 at 5 A g −1 ). • Zinc vanadium oxides (ZVO) with different zinc content are converted from VOOH. • The electrochemical properties of VOOH with different phases are compared. • The appropriate zinc content improves the stability and conductivity of ZVO. • The mechanisms of energy storage and electrode degradation have been elucidated. • Zn 0.36 V 2 O 5 ·nH 2 O exhibits competitive capacity and long-term cyclability. 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 V 2 O 5 ·nH 2 O, Zn 0.25 V 2 O 5 ·nH 2 O, Ca 0.24 V 2 O 5 ·0.83H 2 O, and so on have been exploited owing to their high Zn 2+ storage activity. However, due to the structural disintegration because of the impact of Zn 2+ transportation and poor conductivity, their low capacity, poor cyclability and rate property hinder further utilization. Herein, we report the stable zinc vanadium oxides Zn 0.36 V 2 O 5 ·nH 2 O 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 Zn 2+ , 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 Zn 0.36 V 2 O 5 ·nH 2 O 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.