Influence of cathodic overpotential and zincate concentration on zinc deposition in alkaline solution

摘要

Understanding zinc deposition during charging is important for the development of electrically rechargeable zinc-air batteries. For this purpose, the influences of cathodic overpotential and zincate concentration on zinc deposition in 6 M KOH solution were investigated by electrochemical and morphology characterization. When the zincate concentration is lower than 0.1 M, or the cathodic overpotential is more positive than -30 mV, the first charge-transfer reaction (Zn(OH)(2) + e(-) -> Zn(OH) + OH-) tends to be the rate-determining step. The second charge-transfer reaction (Zn(OH) + e(-) -> Zn + OH-) becomes the rate-determining step at zincate concentration higher than 0.2 M and cathodic overpotentials larger than -50 mV. A low zincate concentration and small cathodic overpotential help suppress dendritic zinc deposition. These results will promote the performance of zinc anodes during the charging of zinc-air batteries.