In‐Situ Gelled Hybrid Polymer‐Ceramic Electrolytes: Empowering Superior Performance and Stability in Lithium‐Sulfur Batteries

ABSTRACT Lithium‐sulfur (Li‐S) batteries offer a compelling alternative to conventional Li‐ion batteries, with their potential for higher energy density and greater sustainability. Despite active industrial efforts toward Li–S commercialization and recent successes in niche markets, broader deployment remains limited by polysulfide shuttling, lithium‐metal instability, and the flammability of ether‐based liquid electrolytes. To address these limitations, a novel in‐situ gelled hybrid polymer‐ceramic electrolyte (GE), POSS‐PEG, is introduced, enabling facile fabrication and delivering high ionic conductivity, electrochemical stability, and enhanced safety. The POSS‐PEG GE significantly reduces polysulfide shuttling and enhances cycling stability compared to traditional liquid electrolyte (LE). Incorporation of the liquid electrolyte into the in situ cross‐linked polymeric network, together with the polar silsesquioxane core, promotes more uniform Li + transport and reduces concentration gradients compared to conventional polymeric electrolytes. Operando and post‐mortem analyses indicate that the GE stabilizes both the S/C cathode–electrolyte interface (CEI) and the Li metal anode, supporting efficient sulfur redox reactions and more uniform Li stripping/ deposition. Consequently, POSS‐PEG delivers improved electrochemical performance across various cell configurations, including pouch cells, maintaining capacity at high current rates and retaining function under mechanical stress. Overall, the POSS‐PEG GE offers a practical path toward safer and longer‐lasting Li–S batteries.