Mitigation of Dendrite Formation on Zinc Electrodes in Mildly Acidic Electrolytes: The Influence of Self-Assembled Graphene Surface Coatings and Electrolyte Additives

The use of zinc electrodes in mildly acidic aqueous batteries remains challenging, partly because of dendrite formation during charge and discharge cycling. This study investigates the influence of reduced graphene oxide surface coatings and electrolyte additives on the stripping/electroplating performance of zinc. Partially and fully coated electrodes are investigated and compared to the performance of a bare zinc surface. The electrolytes consist of zinc sulfate with sodium sulfate and/or sodium acetate as additives. A series of characterization techniques, including cyclic voltammetry, linear sweep voltammetry, electrochemical impedance spectroscopy, chronopotentiometry, and galvanostatic charge and discharge cycling combined with post-mortem scanning electron microscopy, are used to characterize the electrode-electrolyte combinations. The results show that the coatings, in combination with a suitable background electrolyte, greatly improve the reversibility and stability of zinc plating/stripping. A fully coated electrode with a sodium sulfate electrolyte additive achieves almost 450 h of stable operation before failure. The bare zinc electrode under the same conditions, however, already shows severe voltage fluctuations after around 240 h.