LiTFSI salt concentration effect to digest lithium polysulfides for high-loading sulfur electrodes

Sulfur utilization improvement and control of dissolved lithium polysulfide (LiPS; Li₂S_x, 2 < x ≤ 8) are crucial aspects of the development of lithium-sulfur (Li-S) batteries, especially in high-loading sulfur electrodes and low electrolyte/sulfur (E/S) ratios. The sluggish reaction in the low E/S ratio induces poor LiPS solubility and unstable Li₂S electrodeposition, resulting in limited sulfur utilization, especially under high-loading sulfur electrode. In this study, we report on salt concentration effects that improve sulfur utilization with a high-loading cathode (6 mg_sulfur cm⁻²), a high sulfur content (80 wt%) and a low E/S ratio (5 mL g_sulfur⁻¹). On the basis of the rapid LiPS dissolving in a low concentration electrolyte, we established that the quantity of Li₂S electrodeposition from a high Li⁺ diffusion coefficient, referring to the reduction of LiPS precipitation, was significantly enhanced by a faster kinetic. These results demonstrate the importance of kinetic factors for the rate capability and cycle life stability of Li-S battery electrolytes through high Li₂S deposition under high-loading sulfur electrode.