Highly Reversible Phase Transition Endows V6O13 with Enhanced Performance as Aqueous Zinc-Ion Battery Cathode

Aqueous zinc-ion batteries (ZIBs), with favorable merits of high security and low cost, have gained much interest in the energy storage field. However, their development is still in its infancy. Herein, V6O13 is investigated as aqueous ZIB cathodes with excellent Zn2+ storage performance, as compared with VO2 and V2O5. The intrinsic open structure of V6O13 with mixed-valance states of vanadium (V4+/V5+) is favorable to enable fast Zn2+ ion diffusion and improved electronic conductivity, outperforming VO2 and V2O5. Significantly, the highly reversible phase transition of zinc vanadate (Zn0.25V2O5 center dot H2O) can be detected during discharging, which enables the insertion of more Zn2+ ions into the host structure. As a result, V6O13 can exhibit enhanced electrochemical properties, including high capacity and excellent long-term cyclability (206 mA h g(-1) at 10 A g(-1) after 3000 cycles).