Dual-functional in-situ gel polymer electrolyte for high-performance quasi-solid-state Na-S batteries

Sodium-sulfur (Na-S) batteries are believed as the hopeful energy storage and conversion techniques owing to the high specific capacity and low cost. Nevertheless, unstable sodium (Na) deposition/stripping of Na metal anode, low intrinsic conductivity of sulfur cathode, and severe shuttling effect of sodium polysulfides (NaPSs) pose significant challenges in the actual reversible capacity and cycle life of Na-S batteries. Herein, a self-supporting electrode made of nitrogen-doped carbon fiber embedded with cobalt nanoparticles (Co/NC-CF) is designed to load sulfur. Meanwhile, gel polymer electrolyte (GPE) with high ion transfer ability is obtained by in-situ polymerization inside the battery. During the polymerization process, an integrated electrode-electrolyte and a continuous ion-electron conduction network in a composite cathode are constructed inside the Na-S battery. It is noteworthy that the designed GPE demonstrates superior ionic conductivity and effective adsorption of NaPSs that can significantly suppress the shuttle effect. Leveraging the synergistic interplay between the designed GPE and self-supporting cathode, the assembled quasi-solid-state (QSS) Na-S battery exhibits great cycling stability. These experimental results are further corroborated by COMSOL Multiphysics simulations and density functional theory (DFT) calculations, which mechanistically validate the enhanced electrochemical performance. The findings of this study offer new and promising perspectives for advancing the development of next-generation solid-state batteries.