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 at 0.2 A g over 500 cycles and 248 mAh g at 1 A g 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.