The Behavior of Zinc Electrode in Alkaline Electrolytes: I . A Kinetic Analysis of Cathodic Deposition

Abstract

A model for the cathodic electrode activation is developed so as to account for the polarization curves and impedance plots obtained for zinc deposition in alkaline electrolytes. The reaction pattern involves the two-step discharge of zincate ions through an oxide-containing layer whose ionic and electronic conductivities are potential activated. The sharp electrode activation with increasing cathodic polarization is shown to be related to the spreading and thinning of the conductive layer. These phenomena and the concentration of the monovalent intermediate in the layer account for the three timeconstants distinguished in the inductive electrode impedance. The growth of granular compact deposits, favored by trace lead in the electrolyte, is associated with the exmtenee of a uniformly conductive layer on the whole electrode surface. The presence of a fluorinated surfactant (FI 110) inhibits the formation of spongy deposits in close connection with modifications to both the kinetic parameters of reaehons and the geometrical parameters of the conductive layer.

Zinc regeneration in rechargeable zinc-air fuel cells—A review

“…It is clear that the presence of such an autocatalytic reaction step and the interaction of its product, i.e., the intermediate zinc complex ion, with hydrogen and anions such as OH -can lead to multiple steady states of zinc ion thus resulting in instabilities and continuous oscillations of the system. Using this autocatalysis step and interactions between hydrogen and zinc (both cations and anions), the oscillation of the zinc electrode potential observed during zinc deposition at high current densities could be partially explained [76,103,105]. The oscillation was further proved to be caused by a local transient alternating depletion of such electroactive species as zinc and zinc hydroxide ions at the electrode/electrolyte interface.…”

“…) have the advantage of being chemically stable in strong basic electrolytes and can stabilize the grain structure of zinc deposits, hindering the formation of mossy and dendrite deposits through the absorption at rapid-growth sites on the negative electrode surface [73][74][75][76].…”

“…Impedance measurements revealed that during discharging/charging of the Zn electrode in a rechargeable battery system, the additive F1110 helps maintain the compactness of Zn deposits, also eliminates the deleterious effect of spongy Zn formation induced by anodically dissolved zinc [76]. Tetra-alkyl ammonium hydroxide and tetra-alkyl ammonium ethoxide were tested.…”

“…those commonly termed as "dendrites". Hence, studies on the morphology control of zinc deposited from zincate electrolyte, which have been carried out for decades, are still of high importance for the battery/fuel cell field [31,76,88,[96][97][98][99][100][101].…”

“…The EIS results obtained by Cachet et al showed that the steady state of zinc electrode was controlled by the presence of interfacial layers whose geometric properties and conductivity depended upon the electrode polarization [76]. There exists an oxide-containing layer at electrode surface whose ionic and electronic conducting performances are potential activated.…”