Introduction: A molecular-level understanding of the surface chemistry occurring at electrode-electrolyte interfaces (EEIs) during charge transfer processes is necessary to enable the rational design of efficient “beyond-Li ion” energy storage technologies such as Mg-ion batteries. The reversible plating and stripping of Mg²⁺ cations on Mg metal anodes are often accompanied by inefficiencies due to electrolyte decomposition, as well as poor mass- and charge-transport at the solid-electrolyte interphase (SEI) layers. These limitations affect device-level performance and stability. In this work, we studied the effect of aliovalent dopant Al nanoclusters on controlling the charge and mass transfer of Mg²⁺ ions during Mg plating and stripping processes at interfaces.

Methods and Results: We developed a unique multimodal characterization platform that combines controlled deposition of ions and metal clusters (soft- and hard-landing) with in-situ electrochemical impedance spectroscopy (EIS), operando Raman spectroscopy, and in-situ x-ray photoelectron spectroscopy (XPS). Our multimodal platform enabled us to: (i) prepare well-defined electrode interfaces containing specific species of interest; (ii) study the effect of aliovalent doping with Al on mitigating the degradation of electrolyte species during the Mg plating and stripping processes.

Conclusions: A significant change in the overpotential and charge transfer resistance for plating and stripping in the presence of Al doping is revealed by in-situ EIS, whereas operando Raman and in-situ XPS were used to characterize the changes in the structural and chemical state of the SEI layers. In this presentation, we will describe how our multimodal platform enabled us to determine the role of Al clusters at the SEI in modulating interfacial charge transfer kinetics and chemical degradation at Mg battery interfaces.

Keywords: Mg battery, solid-electrolyte interphase, operando spectroscopy