ISBN 9783843942034

978-3-8439-4203-4, Reihe Verfahrenstechnik

Marina Bockelmann
Investigation and prevention of anodic zinc passivation in alkaline zinc-air batteries

84 Seiten, Dissertation Technische Universität Clausthal (2019), Softcover, A5

Zusammenfassung / Abstract

Large-scale rechargeable metal-air batteries and specially the alkaline zinc-air batteries (ZAB) are of particular interest, despite the continuing demand of technological development of this system. They are characterized by a low safety risk and a high specific energy density. They are environmentally friendly, non-toxic and comparatively inexpensive. Despite the numerous advantages of the ZAB, these devices are still far from commercialization, primarily due to their poor cyclic stability and low efficiency. One of the reasons for the short service life of the ZAB is the anodic passivation of the zinc electrode during battery discharge. While anodic zinc dissolution, tetrahydrozincate ions are formed which tend to precipitate as zinc oxide or zinc hydroxide on the surface of the electrode. The resulting passive layer behaves like an insulator and stops the operation of the ZAB. A reactivation of the electrode is not possible according to the current state of knowledge.

The focus of the present work was on the development of a suitable in situ analysis method for the investigation of the passivation process on the zinc electrode. Based on a combination of electrochemical impedance spectroscopy and microscopy, it was possible to detect the starting point of passive film formation for the first time. On the basis of this result, a deeper understanding of the film formation could be gained and an overall mechanism of the complex passivation process could be suggested. Furthermore, the influence of the most important operating parameters of a ZAB, such as temperature, electrolyte composition and convection, on the passivation of the zinc electrode was studied. Therefore, it became possible to choose optimal operating conditions of a ZAB which allow a passivation-free operation of the system. This could also be confirmed within the present work by means of an in-house developed electrically rechargeable ZAB which had a significantly improved service life of over 600 cycles and showed no passivation phenomena due to optimization of operating conditions. Thus, it can be concluded, that this work represents an important step towards the realization of an electrically rechargeable zinc-air battery for energy storage applications.