Unsaturation degree of Fe single atom site manipulates polysulfide behavior in sodium-sulfur batteries.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 40118884.
- Also identified by DOI 10.1038/s41467-025-58114-9 and PMC identifier 11928504.
- Licence recorded as CC BY-NC-ND.
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Abstract
Sodium | |sulfur batteries hold great promise for grid-scale energy storage, yet their performance is hindered by the shuttling and sluggish redox of sulfur species. Herein, we report a strategic design of sulfur hosts modified with coordinatively unsaturated iron single-atom (Fe‒N<sub>x</sub>) for sodium | |sulfur batteries. Utilizing theoretical calculations, geometric descriptor γ (l<sub>Na‒S</sub>/l<sub>Fe‒N</sub>) and electronic descriptor φ (e<sub>g</sub> /t<sub>2g</sub>) simultaneously correlated with the unsaturation degree of Fe‒N<sub>x</sub> site are proposed. A negative correlation between γ and the adsorption strength of sodium polysulfides, along with a positive correlation between φ and the decomposition capability of Na<sub>2</sub>S are established. The Fe‒N<sub>1</sub> sites, with the minimum γ and maximum φ values, are identified as the optimal functional species for optimizing polysulfides behaviors. Sodium | |sulfur batteries utilizing Fe‒N<sub>1</sub> /S positive electrodes deliver improved sulfur utilization (81.4% at 167.5 mA g<sup>‒1</sup>), sustained rate performance (1003.0 mAh g<sup>‒1</sup> at 1675 mA g<sup>‒1</sup>), and stable cycling (83.5% retention over 450 cycles at 3350 mA g<sup>‒1</sup>). Moreover, Fe‒N<sub>1</sub>/S positive electrodes enable sodium | |sulfur pouch cells to deliver a sulfur utilization of 77.4% (1296.9 mAh g<sup>‒1</sup>) at 0.1 A g<sup>‒1</sup>. Our work offers a strategy for designing high-activity, fast redox sulfur positive electrodes and validates the practical potential of sodium | |sulfur batteries.