Proton-assisted mixed-valence vanadium oxides cathode with long-term stability for rechargeable aqueous zinc ion batteries

Abstract

In this work, we developed a rGO assisted vanadium oxide xerogel (abbreviate as VOHG) as cathode material for rechargeable aqueous zinc ion batteries (RA-ZIBs). The VOHG cathode exhibits an ultra-high specific capacity of 625 mA h g−1 at current density of 0.1 A g−1, superior reversibility and a long cycle life with a coulombic efficiency of 100.0% after 10,000 cycles. The VOHG material has mixed valent vanadium ions V4+/V5+and a layer structure with interlayer water. The interlayer water acts as soft support for the VO6 octahedron, forming a large space in the layers for H+/Zn2+ intercalation, which improves the migration rate of Zn2+ due to its charge shielding effect. Protons can move quickly through the interlayer water network by Grotthuss proton transport mechanism. The application of the unique structure of VOHG makes zinc ions battery will be a promising candidate of energy storage device with high-capacity and long cycle stability.