Suppressing Dendrite Growth during Zinc Electrodeposition by PEG-200 Additive

Electrodeposition of zinc at current densities close to the mass transport limit produces needle-like dendrites. Suppressing dendrites is of technological interest to applications in sacrificial corrosion protection coatings and flow batteries. In the present work, we report the use of polyethylene glycol (PEG, M.W. = 200) as an effective electrolyte additive to suppress dendrites during zinc electrodeposition from halide-based electrolytes. Dendrite growth rate is measured as a function of the PEG concentration using in situ optical microscopy, which shows that the dendrite suppression efficacy due to PEG increases with PEG concentration. Polarization experiments on a rotating disk electrode provide system parameters, i.e., the exchange current density and the cathodic transfer coefficient, which confirm that PEG suppresses the zinc electrodeposition kinetics. The kinetic parameters are incorporated into a simple electrochemical model for activation-controlled dendrite propagation. The model predicts an order of magnitude reduction in the zinc dendrite growth rates in the presence of high concentration of PEG (10000 ppm), consistent with experimental findings.