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

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-N-2 moiety (Zn-N-2/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-N-4 center, unsaturated Zn-N-2 center with asymmetric electron distribution has significant advantages in anchoring and activating sodium polysulfides to accelerate the conversion from S-8 to Na2S and reducing the reaction energy barrier of Na2S decomposition. Consequently, Zn-N-2/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-N-4/CF/S (688.0 mAh g(-1)). Moreover, Zn-N-2/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.

Automated summary

In this study, a flexible carbon film implanted with single-atomic Zn-N-2 moiety was constructed as an efficient sulfur host material to improve the redox kinetics and electrical conductivity of sulfur cathode in room-temperature sodium-sulfur batteries.