A Polymer Electrolyte for Rechargeable Magnesium Batteries Synergistically Constructed Based on Deep Eutectic Electrolytes and Polymer Network

ABSTRACT The emerging strategy of combining deep eutectic electrolytes (DEEs) with polymer matrices to construct deep eutectic polymer electrolytes (DEPEs) shows great potential in enhancing the ionic conductivity and electrochemical stability of polymer electrolytes for rechargeable magnesium batteries (RMBs). However, the synergistic interactions between DEEs and polymer networks and their influence on DEPE performance remain insufficiently understood. Here, a new class of DEPEs is developed by combining DEEs formed by MgCl ₂ and 2‐chloro‐ N,N ‐dimethylacetamide (CDMA) with a polymer network formed by poly(ethylene glycol) diacrylate (PEGDA). The effects of the polymer network on the solvation structures of DEEs, ion transport behavior, and the electrode/electrolyte interface are systematically investigated. Compared with DEEs, the polymer network enhances Mg ²⁺ ‐carbonyl coordination in CDMA and effectively suppresses Cl ⁻ migration, thereby optimizing the electrode/electrolyte interface. These enable the DEPEs to exhibit a high magnesium ion transference number (0.665), a high ionic conductivity (3.85 × 10 ⁻⁴ S cm ⁻¹ ), significantly widen the electrochemical stability window of the DEPEs to 2.469 V (compared with 1.653 V for DEEs), enhanced cycling performance, and significantly reduced corrosiveness. Full Mg||Mo ₆ S ₈ cell using these DEPEs excellent cycle stability at 0.1 C. This work provides valuable insights into the design of high‐performance DEPEs for RMBs.