Zinc metal anode plating morphology in mild acidic electrolytes under slow oscillatory flow

Aqueous zinc batteries offer high energy density but are plagued by morphological instabilities, particularly dendritic growth during Zn deposition while charging that can compromise safety and cycle life via internal short circuits and loss of active material. This study investigates the effect of slow, oscillatory electrolyte flow on the morphology of zinc plating in mild acidic electrolytes. We develop and experimentally validate a computationally efficient one-dimensional (1D) electrochemical model to simulate plating dynamics under stagnant, unidirectional, and oscillatory flow conditions. Simulations show that slow uniform and oscillatory flow can maintain the anode surface concentration above a threshold during electrodeposition, eliminating the depletion that causes high overpotential and poor morphology in stagnant electrolytes. Experiments confirm the reduced impedance and dendrite suppression provided by slow flow using voltage measurements and SEM images, respectively. Design maps based on anode surface concentration indicate flow velocities and amplitudes that may provide dendrite-free deposition. In 0.1M electrolytes, stable deposition requires electrode velocities above approximately 0.05 mm/s with oscillation amplitudes greater than half the electrode gap, whereas 0.05M demands substantially higher velocities and amplitudes. Experiments confirm the model-based trends, showing high impedance and dendritic plating at low amplitudes and less than critical flow rates.