Enhanced Reversibility of Mg Plating/Stripping via Solvation Sheath Regulation by a Multidentate Linear Oligoether

Magnesium (Mg) is an abundant resource, and rechargeable Mg metal batteries (RMMBs) could help to achieve a sustainable society. However, practical Mg batteries require electrolyte materials compatible with both positive and negative Mg metal electrodes. Weakly coordinating anion (WCA)‐based electrolytes meet these requirements and have had a groundbreaking impact on this field of research. In this study, the effects of multidentate oligoether additives on the structural characteristics of WCA‐based electrolytes are examined. Integrating a linear oligoether of hexaglyme (G6) is found to be particularly effective at enhancing Mg plating/stripping performance, whereas the corresponding cyclic counterparts impart inferior performance. The combined electrochemical and spectroscopic analyses suggest that changes in the coordination environments of Mg 2+ in solution with a specific amount of G6 are responsible for the enhanced interfacial charge‐transfer kinetics. The results of this study will help guide the design of fully ethereal RMMB electrolytes compatible with highly reactive Mg metal‐negative electrodes.