Controlled Current Deposition of Zinc from Alkaline Solution

Abstract

Electrodeposition of zinc onto foil electrodes from alkaline zincate solutions with direct current results in dendritic or black, porous mossy deposits. Smoother deposits are obtained with a pulsed current source or periodic reversal of current. The nature of the deposit with pulsed charging depends on the current density, the amount of charge passing through the electrolytic cell, the on time, and off time. The optimum values of these parameters are dependent on the cell geometry and the differences between the apparatus used in the present study and a cell containing a secondary zinc electrode are discussed.

Hyper-dendritic nanoporous zinc foam anodes

“…7,9,[16][17][18] The morphology of electrodeposited zinc is dependent on the intermediate product zincate. Precipitation of zincate at the surface interface generally initiates dendritic morphologies at limiting current densities due to non-uniform concentration gradients.…”

“…Historically, it has been limited by morphological uncertainty, which is dependent on local current density and pH. 8 Two typically undesirable regimes are ramification or the formation of dendrites that lead to electrical-short-circuits 9 and precipitation of ZnO 10,11 that can irreversibly passivate a surface. In conventional static zinc systems (composites, pastes and powders), these mechanisms lead to terminal failure, and in flow and flowassisted cells they can be reversed only at the cost of additional system overhead.…”

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

“…Once moss is initiated, the process cannot be reversed; however, this transition can be delayed somewhat by the use of modified charging methods that affect the wavelength and magnitude of the roughness (9). Mossy zinc is ohmically advantaged, so the compact layer's growth stops once the moss becomes the dominant surface feature.…”

“…Arouete's findings (9). When the potential was low and held constant ( < 40 mV) spongy deposits were initiated after an induction time on the order of minutes.…”

“…Ideally, the formation of an even, adherent porous plate is desirable when charging, because the average current density is reduced, and it is possible that the cycle life 9 can be extended. Although normally a decreased current density is beneficial to the cycle life of the battery, mossy zinc is non-adherent, and the capacity loss caused by the detachment of zinc from the cathode far outweighs any possible increase in cycle life (9).…”