Highly Flexible Carbon Film Implanted with Single‐Atomic Zn−N₂ Moiety for Long‐Life Sodium‐Sulfur Batteries

Abstract Room‐temperature sodium‐sulfur (RT Na–S) batteries are regarded as one of promising next‐generation energy storage systems owing to the high theoretical energy density (1274 Wh kg⁻¹) and rich abundance of the raw materials. However, the sluggish redox kinetics and low electrical conductivity of sulfur (S) cathode significantly imped their practical application. Herein, a flexible carbon film implanted with single‐atomic Zn−N₂ moiety (Zn‐N₂/CF) is constructed as the efficient S host material to effectively improve the redox kinetics and electrical conductivity. The theoretical and experimental results show that, compared to Zn−N₄ center, unsaturated Zn−N₂ center with asymmetric electron distribution has significant advantages in anchoring and activating sodium polysulfides to accelerate the conversion from S₈ to Na₂S and reducing the reaction energy barrier of Na₂S decomposition. Consequently, Zn‐N₂/CF/S can retain a reversible capacity of 838.5 mAh g⁻¹ at 0.1 A g⁻¹ after 100 cycles, which is higher than that of Zn‐N₄/CF/S (688.0 mAh g⁻¹). Moreover, Zn‐N₂/CF/S also maintains a long‐term cycling performance with a negligible capacity decay rate of 0.006% per cycle over 4000 cycles at 10 A g⁻¹. This work provides an effective strategy to obtain the flexible carbon film implanted with unsaturated single‐atomic structure, thereby ultimately resulting in high‐performance RT Na–S batteries.