Anodic instability of carbon in non-alkaline Zn–air batteries

Abstract

Although non-alkaline rechargeable Zn–air batteries (RZABs) are promising for energy storage, their chemistry is still underdeveloped and unclear. It was suggested that using Zn(OAc)₂ or Zn(OTf)₂ aqueous solutions as electrolytes enables reversible, corrosion-free charge–discharge processes, but the anodic stability of carbon in these cells has remained poorly studied. We report that CO₂ evolution is manifested during the oxygen evolution reaction in non-alkaline RZABs, which is associated with the corrosion of carbon scaffolds. This corrosion is observed for different electrolyte compositions, such as Zn(OAc)₂, ZnSO₄ and Zn(OTf)₂ solutions of various concentrations. The corrosion rate decreases when the overpotentials during the oxygen evolution reaction are lower. This study underlines the importance of addressing the anodic instability of carbon in non-alkaline RZABs.