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

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 PEOLiTFSI polymer swellable gel as a nanoscale reservoir to trap the polysulfides under lean electrolyte conditions. The PEOLiTFSI 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/g (3.3 mL/g) could deliver a capacity of 1200 mA h/g, 4.6 mA h/cm, and good cycle life. The accumulation of polysulfide reduction products, such as LiS, on the cathode, is identified as the potential mechanism for capacity fading under lean electrolyte conditions.