On the Morphology of Zinc Electrodeposition from Alkaline Solutions

Abstract

The morphology of zinc electrodeposition was investigated from alkaline zincate solutions on single grains of known orientation in polycrystalline zinc electrodes under potentiostatic control. The effect of overpotential, solution composition, and substrate orientation were examined. The deposition morphology was observed with a scanning electron microscope. It was found possible to disrupt the deposition repeatedly for microscopic observation, and then continue deposition. At low overpotential (50 mV) epitaxial layer type growth was observed; the width of the macrosteps increased linearly with time. A theory explaining the linear step widening is proposed, which can also account for the observed effect of substrate orientation. At 100 mV, “boulders” were observed, not all of which were epitaxial with the substrate. They are suggested to be originated by nucleation. The boulder density per cm2 is first sharply increasing, then slowly decreasing with time. A statistical calculation for this is given, based on the model that large boulders consume the smaller ones. With further deposition a small fraction (ca. 0.1%) of the boulders develop into dendrites, their number being limited by the available total current. Experiments were carried out to differentiate between over‐potential and current control of morphology; overpotential was found to be the critical variable.

<i>Operando</i> X-ray Fluorescence Imaging for Zinc-based Secondary Batteries

“…The zinc dendrite formation on the reduction process was employed according to the literatures under a potentiostatic condition at ¹0.24 V vs. Zn/Zn 2+ for 10 mAh. 8,9 The oxidation process was employed at a constant current of 10 mA as seen in general battery operation.…”

Studies on the development of mossy zinc electrodeposits from flowing alkaline electrolytes

“…The impurity stabilizes the thermodynamically unstable host nucleus and lowers the overpotential for metal deposition (85,86). However, most impurities lower the overpotential for detrimental side reactions, particularly hydrogen evolution.…”

“…In a study by Bockris and co-workers (86), electrochemistry was performed on well characterized zinc surfaces which contained steps oriented along the {0001} and {llOO} planes at varying angles to the perpendicular axis. It was postulated that if a high index plane could be formed from steps bounded by dislocations, then the widening of steps with time could be predicted.…”

Studies of micromorphology and current efficiency of zinc electrodeposited from flowing chloride electrolytes

“…After the passage of several coulombs, the deposit appeared striated, or had fishnet structures or dendrites (13,16,53).…”