Aliphatic saturated sulfones C8–C10 as new electrolyte solvents for Li batteries

The search for new electrolytes (including solvents and salts) is essential for the development of lithium batteries. The sulfone family of solvents has gained significant attention due to their high electrochemical and thermal stability. In this study, we have explored the potential application of aliphatic non-cyclic sulfones with C8 to C10 carbon chains as electrolyte solvents for lithium batteries ((i-C₄H₉)₂SO₂, (i-C₅H₁₁)₂SO₂, and (i-C₄H₉) (i-C₅H₁₁)SO₂). These sulfones have lower melting points in comparison with well-known sulfolane, with eutectic melting points below 0 °C. The experimental phase diagram of (i-C₄H₉)₂SO₂ and (i-C₅H₁₁)₂SO₂ aligns well with predictions based on an ideal liquid solution model, assuming no formation of solid solutions. This approach enables the estimation of eutectic coordinates for other compounds in this class. Here, we thoroughly characterize sulfone-based electrolytes, investigating their electrochemical stability, ionic conductivity, and thermal stability. The oxidation stability and oxidation mechanism of considered C8-C10 sulfones were investigated within the framework of density functional theory calculations, as well as the solvation shell for Li⁺. Overall, LiFePO₄//Li cells using these electrolytes demonstrate stable cycling at 75 °C.