Long-Life Zinc/Vanadium Pentoxide Battery Enabled by a Concentrated Aqueous ZnSO₄ Electrolyte with Proton and Zinc Ion Co-Intercalation

Rechargeable aqueous zinc/vanadium pentoxide (Zn/V2O5) battery chemistry has recently attracted a great attention due to its high safety, material abundance, cost effectiveness, and desirable energy density. However, the reaction mechanism of V2O5 in an aqueous electrolyte remains a topic of discussion, and the limited life span resulting from the active materials dissolution hinders the further development of the Zn/V2O5 battery. Here, we report a long-life aqueous Zn/V2O5 battery using a simply ball-milled V2O5 cathode, a concentrated aqueous ZnSO4 electrolyte, and a metallic Zn anode. Electrochemical, structural, and spectroscopic analyses reveal that the V2O5 electrode experiences a highly reversible proton (H+) and Zn2+ co-intercalation mechanism in aqueous media, which differs from the conventional cognition that Zn2+ ion as the only charge carrier inserts into the V2O5 host. The electrolyte-involved (dis)appearance of zinc sulfate hydroxide on the electrodes’ surface caused by H+ (de)intercalation has also been clarified. In addition, the optimized 3 M ZnSO4 electrolyte can not only suppress the dissolution of the V2O5 cathode but also enhance the stability of the Zn anode, thereby enabling the stable operation of the Zn/V2O5 battery with a reversible capacity of 357 mAh g–1 after 2000 cycles without obvious decay at 2.0 A g–1. This work opens up frontiers in the mechanism insight and electrolyte formulation for aqueous Zn batteries.