Sulfolane-modified PEG-based aqueous electrolytes for high-performance rechargeable magnesium-ion batteries

Sulfolane plasticizes PEG-based electrolyte for aqueous Mg-ion batteries. • Sulfolane modulates solvent microenvironment and relieves PEG chain entanglement. • Balanced electrolyte presents wide ESW, low viscosity and high ionic conductivity. • V 2 O 5 //PTCDI full cell delivers improved capacity and superior cycling stability. Aqueous magnesium-ion batteries offer a safe, low-cost, and sustainable energy storage solution, yet their development is impeded by the narrow electrochemical stability window (ESW) of conventional aqueous electrolytes. Although polyethylene glycol (PEG)-based electrolytes provide an expanded ESW, their high viscosity and low ionic conductivity severely limit ionic transport. Herein, sulfolane is introduced as a plasticizer to regulate the physicochemical properties of PEG400-based electrolytes. Across the tested PEG/SUL compositions, sulfolane incorporation substantially reduces electrolyte viscosity and enhances ionic conductivity, with the conductivity increasing from 480 μS cm −1 to 3390 μS cm −1 , while the selected PEG/SUL-11@20%H 2 O electrolyte retains a broad ESW of approximately 3.570  V . Raman and 1 H NMR analyses suggest that the sulfonyl groups in sulfolane interact with PEG400 chains, thereby modifying the local PEG chain environment and mitigating chain entanglement. Considering the trade-off among ESW, viscosity, ionic conductivity, and electrode compatibility, PEG/SUL-11@20%H 2 O was selected as a balanced formulation. The V 2 O 5 //PTCDI full cell assembled with the selected electrolyte delivers a discharge specific capacity of 147.7 mAh g −1 at 100 mA g −1 and retains 85% of its capacity after 600 cycles, demonstrating promising capacity and stable cycling performance. This sulfolane plasticization strategy effectively addresses the conductivity limitation of PEG-based aqueous electrolytes and provides a promising route toward advanced electrolytes for aqueous magnesium-ion batteries. Download: Download high-res image (545KB) Download: Download full-size image