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 PEO₁₀LiTFSI polymer swellable gel as a nanoscale reservoir to trap the polysulfides under lean electrolyte conditions. The PEO₁₀LiTFSI 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_E/g_S (3.3 mL_E/g_S) could deliver a capacity of 1200 mA h/g, 4.6 mA h/cm², and good cycle life. The accumulation of polysulfide reduction products, such as Li₂S, on the cathode, is identified as the potential mechanism for capacity fading under lean electrolyte conditions.