An amorphous hydrated vanadium oxide induced by Zn 2+ intercalation in Mg-ion inserted V 2 O 5 · n H 2 O (MgVOH) is developed as a high-performance cathode for ZIBs. In particular, zinc pyrovanadate as the product of the second phase transition is found to suppress the dissolution issue of the vanadium species for the cathode to facilitate long lifespan.