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

Li, Xia; Banis, Mohammad; Lushington, Andrew; Yang, Xiaofei; Sun, Qian; Zhao, Yang; Liu, Changqi; Li, Qizheng et al. · Nat Commun · 2018

basic_science · Level V

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Abstract

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 Li<sub>2</sub>S without the formation of linear polysulfides. Based on this, we demonstrate the cyclability of conventional cyclo-S<sub>8</sub> 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<sup>-2</sup>. This research demonstrates promising performance of lithium-sulfur pouch cells in a carbonate-based electrolyte, indicating potential application in the future.