Solvation Interactions in Water–DMSO Electrolyte Systems for Enhanced Aqueous Lithium Battery Performance

Hybrid electrolyte solutions composed of water and water-miscible organic solvents have gained attention for their extended electrochemical stability window, nonflammability, high ionic conductivity, and cost-effectiveness. Among them, dimethyl sulfoxide (DMSO) is a particularly attractive cosolvent due to its high dielectric constant, strong hydrogen-bonding ability, low volatility, and excellent chemical stability. When mixed with water, DMSO disrupts the native hydrogen-bond network, significantly altering key physicochemical properties such as viscosity, density, dielectric constant, and water activity─all of which are highly sensitive to composition. Despite their potential, the behavior of water-DMSO electrolytes under high salt concentrations and their effects on electrode performance remain underexplored. Here, we investigated nearly saturated LiClO₄ solutions in water-DMSO mixtures, combining electrochemical testing with NMR, Raman spectroscopies, and theoretical modeling to reveal solvation structures and ion-solvent interactions. We further evaluated how these electrolyte solution compositions impact the electrochemical performance of LiMn₂O₄ cathodes and TiO₂ anodes. These insights highlight the promise of DMSO-based hybrid electrolyte solutions for advancing safe and high-performance aqueous lithium battery technologies.