High-performance polymer electrolytes for rechargeable magnesium batteries based on ether-based liquid electrolytes and crosslinked polymers.

Developing polymer electrolytes (PEs) with high ionic conductivity and compatibility with Mg metal anodes remains a key challenge for solid-state rechargeable magnesium batteries (RMBs). Herein, two PEs, G3-PE1 and G4-PE1, were prepared by immobilizing highly active MgCl2-AlCl3-triethylene glycol dimethyl ether (MgCl2-AlCl3-G3) and MgCl2-AlCl3-tetraethylene glycol dimethyl ether (MgCl2-AlCl3-G4) liquid electrolytes within crosslinked polymer networks, respectively. Benefiting from the retention of the solvation structure of the liquid electrolytes and the structural support provided by the crosslinked polymer networks, both G3-PE1 and G4-PE1 exhibited high ionic conductivity and stable electrochemical performance. At 30 °C, the ionic conductivities of G3-PE1 and G4-PE1 reached 2.14 × 10-3 and 1.07 × 10-3 S cm-1, respectively, with corresponding Mg2+ transference numbers of 0.5801 and 0.4267. Moreover, Mg//Mg symmetric cells employing these PEs maintained stable cycling for over 1500 h at a current density of 25 μA cm-2. Compared with G4-PE1, G3-PE1 exhibited weaker Mg2+-ether coordination, resulting in superior electrochemical performance. The Mo6S8//G3-PE1//Mg full cell delivers a discharge capacity of 54.6 mAh g-1 after more than 350 cycles at 0.1C, demonstrating excellent cycling stability. Immobilizing highly active liquid electrolytes within crosslinked polymer networks therefore provides an effective route for developing high-performance PEs for RMBs.