A chemo-mechanical regulated flexible-rigid binder enables high-rate Na-S batteries

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, active-material 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 chemo-mechanical regulation through a dynamic flexible-rigid binder network as an effective design strategy for high-energy Na-S batteries.