Electrolyte-Dependent Interphase Evolution Governs Galvanic Zinc Plating–Stripping Reversibility Revealed by In Operando EQCM-D

The Zn plating–stripping process governs the reversibility and cycling stability of aqueous zinc-ion batteries (ZIBs), yet how electrolyte chemistry shapes interphase evolution remains poorly understood. Here, in operando electrochemical quartz crystal microbalance with dissipation monitoring (EQCM-D) is employed to investigate Zn plating and stripping in ZnSO4 (ZSO), Zn(OTf)2 (ZOf), and Zn(ClO4)2 (ZCO) electrolytes over a concentration range of 0.5–2.0 M. Distinct electrolyte-dependent interphase evolution pathways are identified. ZCO and concentrated ZSO electrolytes form rigid interphases but remain susceptible to parasitic mass loss, whereas ZOf electrolytes develop viscoelastic interphases through the formation of alkaline byproducts and an anion-containing SEI-like layer. Quantitative analyses of interfacial mass, mass per electron (MPE), and residual mass percentage (RMP) reveal that 0.5 M ZCO shows the highest apparent Zn deposition efficiency, while the 0.5 and 1.0 M ZOf electrolytes leave the least residual mass after stripping in spite of the more extensive interphase formation. These results suggest that the deposition efficiency and the removal of the interphase are not directly correlated but are governed by different interphase evolution pathways. This work provides a mechanistic framework linking electrolyte chemistry to interphase formation and Zn redox behavior, offering design principles for advanced aqueous ZIB electrolytes.