Abstract
The search for safe electrolytes to promote the application of lithium-sulfur (Li-S) batteries may be supported by the investigation of viscous glyme solvents. Hence, electrolytes using nonflammable tetraethylene glycol dimethyl ether added by lowly viscous 1,3-dioxolane (DOL) are herein thoroughly investigated for sustainable Li-S cells. The electrolytes are characterized by low flammability, a thermal stability of ∼200 °C, ionic conductivity exceeding 10(-3) S cm(-1) at 25 °C, a Li(+) transference number of ∼0.5, electrochemical stability window from 0 to ∼4.4 V vs Li(+)/Li, and a Li stripping-deposition overpotential of ∼0.02 V. The progressive increase of the DOL content from 5 to 15 wt % raises the activation energy for Li(+) motion, lowers the transference number, slightly limits the anodic stability, and decreases the Li/electrolyte resistance. The electrolytes are used in Li-S cells with a composite consisting of sulfur and multiwalled carbon nanotubes mixed in the 90:10 weight ratio, exploiting an optimized current collector. The cathode is preliminarily studied in terms of structure, thermal behavior, and morphology and exploited in a cell using standard electrolyte. This cell performs over 200 cycles, with sulfur loading increased to 5.2 mg cm(-2) and the electrolyte/sulfur (E/S) ratio decreased to 6 μL mg(-1). The above sulfur cathode and the glyme-based electrolytes are subsequently combined in safe Li-S batteries, which exhibit cycle life and delivered capacity relevantly influenced by the DOL content within the studied concentration range.