A Chemo-Mechanical Regulated Flexible-Rigid Binder Enables High-Rate Na-S Batteries

Abstract

Room temperature sodium-sulfur (RT Na-S) batteries are promising candidates for low-cost, high-energy-density energy storage. However, severe cathode volume expansion and polysulfide shuttling induce electrode pulverization, activematerial loss, and large electrochemical polarization, resulting in poor rate capability and limited cycling stability. Herein, we report a dynamic flexible-rigid composite binder (PTOG-PAA) that simultaneously regulates the mechanical stability and interfacial sulfur chemistry of RT Na-S cathodes. The binder integrates a flexible poly(thiourea-oxidized glutathione) (PTOG) network with rigid poly(acrylic acid) (PAA) through cooperative hydrogen bonding and covalent crosslinking, enabling efficient stress relaxation while preserving structural robustness. The resulting three-dimensional network exhibits strong adhesion to sulfur electrodes, delivering an average peel strength of 0.743 N, over 15 times higher than that of commercial PVDF. More importantly, the PTOG-PAA binder suppresses electrochemical polarization by facilitating sulfur redox kinetics and maintaining sulfur confinement during repeated volume fluctuations. Consequently, RT Na-S batteries employing the PTOG-PAA binder deliver a high initial discharge capacity of 1525.00 mAh g -1 at 0.1 A g -1 and retain 205 mAh g -1 after 13,300 cycles at 5 A g -1 with an ultralow capacity decay of only 0.037 ‰ per cycle. This work establishes cooperative chemomechanical regulation through a dynamic flexible-rigid binder network as an effective design strategy for high-energy Na-S batteries.