Low-Coordinated Zn–N₂ Sites as Bidirectional Atomic Catalysis for Room-Temperature Na–S Batteries

Abstract

The rational design of advanced catalysts for sodium–sulfur (Na–S) batteries is important but remains challenging due to the limited understanding of sulfur catalytic mechanisms. Here, we propose an efficient sulfur host consisting of atomic low-coordinated Zn–N2 sites dispersed on N-rich microporous graphene (Zn–N2@NG), which realizes state-of-the-art sodium-storage performance with a high sulfur content of 66 wt %, high-rate capability (467 mA h g–1 at 5 A g–1), and long cycling stability for 6500 cycles with an ultralow capacity decay rate of 0.0062% per cycle. Ex situ methods combined with theoretical calculations demonstrate the superior bidirectional catalysis of Zn–N2 sites on sulfur conversion (S8 ↔ Na2S). Furthermore, in situ transmission electron microscopy was applied to visualize the microscopic S redox evolution under the catalysis of Zn–N2 sites without liquid electrolytes. During the sodiation process, both surface S nanoparticles and S molecules in the mircopores of Zn–N2@NG quickly convert into Na2S nanograins. During the following desodiation process, only a small part of the above Na2S can be oxidized into Na2S x . These results reveal that, without liquid electrolytes, Na2S is difficult to be decomposed even with the assistance of Zn–N2 sites. This conclusion emphasizes the critical role of liquid electrolytes in the catalytic oxidation of Na2S, which was usually ignored by previous works.

Rational Design of Janus Metal Atomic‐Site Catalysts for Efficient Polysulfide Conversion and Alkali Metal Deposition: Advances and Prospects

“…Apart from the oversaturated M‐N 5 configuration, the unsaturated M‐N x ( x < 4) form has also attracted significant attention in promoting polysulfide conversion reactions. [ 169–175 ] For instance, Liu et al. reported that the asymmetrically coordinated Fe−N 3 C 2 −C structure could generate additional π‐bonds with LiPSs via activating d x2−y2 and d xy orbital, which accelerates the d−p orbital hybridization and offers strong chemical adsorption for LiPSs.…”

Defect engineering of a TiO2 anatase/rutile homojunction accelerating sulfur redox kinetics for high-performance Na–S batteries

“…18 However, the weak physical interaction between the nonpolar carbon matrix and polar NaPSs makes it difficult to effectively suppress NaPSs diffusion, leading to the unfavorable shuttle effect and abysmal capacity decay. 19 To obtain a superior S cathode, polar materials with strong polar–polar interaction toward NaPSs are proposed, such as oxides, 20,21 sulfides, 22,23 and transition metal nanoclusters/single atoms, 24–28 where a strong polar chemical interaction is conducive to anchor NaPSs and catalyze their rapid conversion, which is critical to suppress the shuttle effect and improve the cycling stability of the S cathode. Li et al reported that Y single-atom catalysts with a Y-N 4 structure were beneficial for the chemical affinity of NaPSs and lowered the conversion kinetics.…”

Intercalation-type catalyst for non-aqueous room temperature sodium-sulfur batteries

“…Inspired by the developments of lithium-sulfur batteries, including the hybrid strategies of TiS 2 , Mo 6 S 8, and S 17 , 18 , intensive research efforts have been focused in the Na-S field, such as the combination of conductive carbon and sulfur, modification of separators with carbon, and development of sulfides cathode 19 – 26 . These systems have illustrated decent electrochemical performance, but only with a low sulfur loading (<2 mg cm −2 ).…”