A high-energy sulfur cathode in carbonate electrolyte by eliminating polysulfides via solid-phase lithium-sulfur transformation

Carbonate-based electrolytes demonstrate safe and stable electrochemical performance in lithium-sulfur batteries. However, only a few types of sulfur cathodes with low loadings can be employed and the underlying electrochemical mechanism of lithium-sulfur batteries with carbonate-based electrolytes is not well understood. Here, we employ in operando X-ray absorption near edge spectroscopy to shed light on a solid-phase lithium-sulfur reaction mechanism in carbonate electrolyte systems in which sulfur directly transfers to Li2S without the formation of linear polysulfides. Based on this, we demonstrate the cyclability of conventional cyclo-S8 based sulfur cathodes in carbonate-based electrolyte across a wide temperature range, from −20 °C to 55 °C. Remarkably, the developed sulfur cathode architecture has high sulfur content (>65 wt%) with an areal loading of 4.0 mg cm−2. This research demonstrates promising performance of lithium-sulfur pouch cells in a carbonate-based electrolyte, indicating potential application in the future.
Carbonate-based electrolytes can impart advantages in lithium sulfur batteries, but performance is often limited by incompatibility with sulfur-based cathodes. Here the authors elucidate a mechanism for conversion of sulfur to lithium sulfide and demonstrate improved performance in a Li-S cell.