Combined\nEffect of Dissolved Oxygen and pH in Aqueous\nElectrolytes on Zn-Anode Corrosion Behavior in Aqueous Zn-Ion Batteries

Aqueous Zn-ion batteries (AZIBs) have recently emerged\nas an appealing\noption for grid scale energy storage due to their distinct advantages\nin safety, cost, and materials sustainability. However, cycle instability\ncaused by the interactions between Zn-anode and electrolyte solutions\n(aka Zn corrosion) has been a critical issue hindering the commercial\ndevelopment of AZIBs. To bridge this technical gap, we herein present\na fundamental study to delineate the important role that the much-neglected\ndissolved oxygen played in Zn anode corrosion reaction along with\npH. Oxygen reduction reaction (ORR) is proposed as a parallel pathway\nto the commonly perceived hydrogen evolution reaction (HER) in the\nZn-anode corrosion mechanism. To prove this new ORR mechanism, we\nsystematically dissolved oxygen and pH in the model ZnSO<sub>4</sub> electrolyte along with current density/polarity and examine the\nresultant surface morphologies, compositions, gas evolution, electrode\noverpotential, and cycle stability of Zn-anode. We conclude that the\ndissolved oxygen-dependent ORR pathway can compete with the pH-dependent\nHER pathway in the formation of the surface passive layer, making\na marked impact on the overpotential and stability of the Zn-anode.\nThe lowest overpotential and longest cycle stability are observed\nin a ZnSO<sub>4</sub> electrolyte with the lowest dissolved oxygen.