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Investigation of the Anode-Electrolyte Interface in a Magnesium Full-Cell with Fluorinated Alkoxyborate-Based Electrolyte

By Roy, Ananyo; Bhagavathi Parambath, Vinayan; Diemant, Thomas; Neusser, Gregor; Kranz, Christine; Behm, R. Jürgen; Li, Zhenyou; Zhao-Karger, Zhirong; Fichtner, Maximilian
Published in Batteries & Supercaps 2022


Abstract Magnesium (Mg) anode-electrolyte interaction is not trivial and investigation of the interfacial process can be helpful for the development of Mg batteries. In this work, we studied the Mg metal anode cycled in a chloride (Cl)-free magnesium tetrakis (hexafluoroisopropyloxy) borate electrolyte using a full-cell configuration with TiS2 model cathode. Electrochemical measurements and structural analysis of the cathode showed reversible de-/magnesiation of TiS2 with some entrapment of irreversibly bound Mg2+. Electrochemical impedance spectroscopy (EIS) was applied to analyze the Mg-electrolyte interaction in a three-electrode system. The results showed a rapid increase in charge transfer resistance on the anode side with increasing resting time. In contrast, we observed a significant drop in the charge transfer impedance upon cycling along with the appearance of an additional semi-circle, which suggested to the development of a solid interphase. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) corroborated the EIS results and confirmed the solid interphase layer formation, in which MgF2 was identified as the primary species contributing to its formation. The current study provides fundamental insights into the interfacial phenomena between the metallic Mg anode and Cl-free electrolyte by highlighting the role played by the formed interphase on the reversible Mg stripping and plating in a Mg full-cell.

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