Superionic Quasi-Solid-State Electrolyte for Rechargeable Magnesium–Oxygen Batteries

Limited by their life span and capacity, magnesium–oxygen batteries have not reached their full potential. We present a quasi-solid-state electrolyte (QSSE) that significantly enhances their performance. This QSSE combines an optimum amount of polyvinylidene fluoride hexafluoropropylene (PVDF-HFP), succinonitrile (SN) as a plasticizer, and magnesium triflate (Mg(OTf)2) as the salt with the high-conductivity ionic liquid (IL) 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr14TFSI), a magnesium ion mobility booster. The resulting low activation energy (0.215 eV) and high room-temperature ionic conductivity (2.6 mS cm–1) of the optimized QSSE facilitate rapid and efficient magnesium-ion transport. Paired with Ru nanoparticle-decorated multiwalled carbon nanotube (Ru/CNT) cathode catalysts, this QSSE-based Mg–O2 battery achieves a remarkable cyclability of 94 cycles at 100 mA g–1. This synergistic combination leads the way for commercially viable Mg–O2 batteries with exceptional stability and high capacity, advancing the path toward sustainable and high-performance energy solutions.