Improving Lithium-Sulfur Battery Performance under Lean Electrolyte through Nanoscale Confinement in Soft Swellable Gels.

Chen, Junzheng; Henderson, Wesley A; Pan, Huilin; Perdue, Brian R; Cao, Ruiguo; Hu, Jian Zhi; Wan, Chuan; Han, Kee Sung et al. · Nano Lett · 2017

basic_science · Level V

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Abstract

Li-S batteries have been extensively studied using rigid carbon as the host for sulfur encapsulation, but improving the properties with a reduced electrolyte amount remains a significant challenge. This is critical for achieving high energy density. Here, we developed a soft PEO<sub>10</sub>LiTFSI polymer swellable gel as a nanoscale reservoir to trap the polysulfides under lean electrolyte conditions. The PEO<sub>10</sub>LiTFSI gel immobilizes the electrolyte and confines polysulfides within the ion conducting phase. The Li-S cell with a much lower electrolyte to sulfur ratio (E/S) of 4 g<sub>E</sub>/g<sub>S</sub> (3.3 mL<sub>E</sub>/g<sub>S</sub>) could deliver a capacity of 1200 mA h/g, 4.6 mA h/cm<sup>2</sup>, and good cycle life. The accumulation of polysulfide reduction products, such as Li<sub>2</sub>S, on the cathode, is identified as the potential mechanism for capacity fading under lean electrolyte conditions.