Understanding H<sub>2</sub> Evolution Electrochemistry to Minimize Solvated Water Impact on Zinc‐Anode Performance
Fuhua Yang, Jodie A. Yuwono, Junnan Hao, Jun Long, Libei Yuan, Yanyan Wang, Sailin Liu, Yameng Fan, Shiyong Zhao, Kenneth Davey, Zaiping Guo
Abstract
Abstract H 2 evolution is the reason for poor reversibility and limited cycle stability with Zn‐metal anodes, and impedes practical application in aqueous zinc‐ion batteries (AZIBs). Here, using a combined gas chromatography experiment and computation, it is demonstrated that H 2 evolution primarily originates from solvated water, rather than free water without interaction with Zn 2+ . Using linear sweep voltammetry (LSV) in salt electrolytes, H 2 evolution is evidenced to occur at a more negative potential than zinc reduction because of the high overpotential against H 2 evolution on Zn metal. The hypothesis is tested and, using a glycine additive to reduce solvated water, it is confirmed that H 2 evolution and “parasitic” side reactions are suppressed on the Zn anode. This electrolyte additive is evidenced to suppress H 2 evolution, reduce corrosion, and give a uniform Zn deposition in Zn|Zn and Zn|Cu cells. It is demonstrated that Zn|PANI (highly conductive polyaniline) full cells exhibit boosted electrochemical performance in 1 M ZnSO 4 –3 M glycine electrolyte. It is concluded that this new understanding of electrochemistry of H 2 evolution can be used for design of relatively low‐cost and safe AZIBs for practical large‐scale energy storage.