Abstract
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 LiClO 4 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 LiMn 2 O 4 cathodes and TiO 2 anodes. These insights highlight the promise of DMSO-based hybrid electrolyte solutions for advancing safe and high-performance aqueous lithium battery technologies.