Use of DMSO as a co-solvent for aqueous lithium-ion batteries

Aqueous electrolytes for lithium-ion batteries offer a safer and more environmentally friendly alternative to flammable organic electrolytes. One of the main challenges, however, is their narrow electrochemical stability window, which is typically widened by using highly concentrated salts, sometimes combined with organic solvents. Dimethyl sulfoxide (DMSO) stands out among organic solvents used in this context due to its affordability, low toxicity, and safe handling. Additionally, DMSO and water form solutions that remain in the liquid state at extremely low temperatures (down to -130 °C). In this study, we designed and characterized three electrolytes by mixing water and DMSO and incorporating lithium bis(fluorosulfonyl)imide (LiFSI) at three different concentrations. The resulting electrolytes exhibited exceptional thermal and electrochemical stability. Furthermore, we provided a detailed analysis of their solvation structure, intermolecular interactions and transport properties. Finally, we evaluated these electrolytes in a full-cell configuration with LiTi₂(PO₄)₃ and LiMn₂O₄, testing their performance at room temperature (100 cycles, 1.5 V, 40 Wh kgAM⁻¹, where AM stands for active mass, and refers to the sum of the active masses of both anode and cathode active materials) and at -10 °C (50 cycles, 1.3 V, 15 Wh kgAM⁻¹).