Functional layer on sulfurized polyacrylonitrile enhancing Na+ de-solvation and transportation for high rate and long life sodium-sulfur batteries

Rechargeable sulfurized polyacrylonitrile (SPAN)-based room temperature sodium-sulfur (RT Na/SPAN) batteries, which can operate stably at room temperature, are highly sought after due to the high coulombic efficiency, excellent reversibility and cycling stability. However, the practical battery performance of the Na/SPAN system is fundamentally limited by sluggish interfacial kinetics, particularly hindered Na + transport and electron transfer at electrode–electrolyte interface. Herein, this study addresses these challenges through a low-temperature (180 ℃) polymeric carbon encapsulation strategy, which strategically constructs a polyfuran-rich amorphous carbon(AC) coating on SPAN microparticles (SPAN@AC). This synergistic mechanism operates through conjugated backbones that facilitate efficient electron transport, while the dual role of oxygen which providing strong Na + coordination and weak bonding interactions, thereby simultaneously accelerating charge transfer and ion-desolvation kinetics at the interface. These strategies effectively mitigate interfacial kinetic limitations in sodium-ion batteries, resulting in improved cycling durability and rate capability during practical battery testing. Hence, the SPAN@AC electrode delivered a reversible capacity of 400 mAh g −1 composite at 0.2 A g −1 over 500 cycles and 248 mAh g −1 composite at 1 A g −1 over 750 cycles. This study develops a new approach to enhance SPAN’s electrochemical properties, thereby establishing its viability as a high-performance cathode material for practical room temperature sodium-sulfur battery applications.