Electrochemical Stress Analysis of Zinc Electrodeposition and Interfacial Instabilities during Anode Reactions in Aqueous Batteries

We investigate surface transformations and structural evolutions during the electrodeposition of Zn on textured polycrystalline Au surfaces using in situ electrochemical stress measurements. Zn electrodepositions at anodes of aqueous Zn batteries (AZBs) are crucial to the design and application of these batteries as an integrated grid-scale storage solution. Controlling the competing hydrogen evolution reaction (HER) and the deposition of Zn remains challenging in mildly acidic media. Our electrochemical stress analysis focuses on the early stages of nucleation of Zn on polycrystalline Au surfaces in different acidic solutions of ZnSO 4 and H 2 SO 4 mixtures. We will discuss features in electrochemical stress analysis assigned to the underpotential deposition (UPD) of Zn on model Au surfaces. The observed compressive features are particularly prominent around neutral pHs. We assign these features to the formation of an ordered adlayer or intermetallic Zn-Au phase before Zn bulk deposition. At more negative potentials, where Zn overpotential deposition (OPD) occurs, the magnitude of compressive stress increases substantially. The stress generated with Zn deposition corresponds to the amount of Zn deposited. Variations in scan rate and potential range significantly influence stress magnitude and patterns. During Zn stripping, stress response shows significant hysteresis as the surface transitions to a less compressive state. Repeated deposition and stripping of Zn on Au model surfaces leads to instability in stress behavior and diminished electrochemical response. This study investigates the UPD and OPD of Zn on Au model surfaces, highlighting the role of solution pH and surface structure in mediating the HER and electrodeposition of Zn. The results show how surface stresses correlate with distinct stages of Zn deposition and explain the instability of the deposition process. Our analysis provides insight into Zn electrodeposition dynamics in anodes of aqueous batteries, crucial for the development of high-performance AZBs.