Effect of Chloride Ions on the Electrochemical Performance of Magnesium Metal-Organic-Frameworks-Based Semi-Solid Electrolytes

The majority of research on magnesium (Mg) electrolytes has focused on enhancing reversible Mg deposition, often employing chloride-containing electrolytes. However, there is a notable gap in the literature regarding the influence of chloride ions in semi-solid Mg electrolytes. In this study, we systematically explore the impact of chloride ions on Mg deposition/dissolution on a copper (Cu) anode using a semi-solid electrolyte composed of Mg-based mixed metal-organic frameworks, MgCl2 and Mg[TFSI]2. We separate the Mg deposition/dissolution process from changes in the anode's surface morphology In this respect, the morphological and compositional transformations in the electrolyte and electrode following galvanostatic cycling are meticulously investigated. Initial potential cycling reveals the feasibility of Mg deposition/dissolution on Cu electrodes, albeit with reduced reversibility in subsequent cycles. Extending the upper potential limit to 4.0 V vs. Mg/Mg2+ enhances Mg dissolution, attributed to chloride ions facilitating Cu surface dissolution. Our findings provide insights into optimizing semi-solid electrolytes for advanced Magnesium battery technologies.