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<p>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><i>x</i></sub>) for sodium | |sulfur batteries. Utilizing theoretical calculations, geometric descriptor <i>γ</i> (<i>l</i><sub>Na‒S</sub>/<i>l</i><sub>Fe‒N</sub>) and electronic descriptor <i>φ</i> (<i>e</i><sub>g</sub> /<i>t</i><sub>2g</sub>) simultaneously correlated with the unsaturation degree of Fe‒N<sub><i>x</i></sub> site are proposed. A negative correlation between <i>γ</i> and the adsorption strength of sodium polysulfides, along with a positive correlation between <i>φ</i> and the decomposition capability of Na<sub>2</sub>S are established. The Fe‒N<sub>1</sub> sites, with the minimum <i>γ</i> and maximum <i>φ</i> 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.</p>

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Unsaturation degree of Fe single atom site manipulates polysulfide behavior in sodium-sulfur batteries

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年3月21日

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  • Wanqing Song,
  • Zhenzhuang Wen,
  • Xin Wang,
  • Kunyan Qian,
  • Tao Zhang,
  • Haozhi Wang,
  • Jia Ding,
  • Wenbin Hu

摘要

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‒Nx) for sodium | |sulfur batteries. Utilizing theoretical calculations, geometric descriptor γ (lNa‒S/lFe‒N) and electronic descriptor φ (eg /t2g) simultaneously correlated with the unsaturation degree of Fe‒Nx 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 Na2S are established. The Fe‒N1 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‒N1 /S positive electrodes deliver improved sulfur utilization (81.4% at 167.5 mA g‒1), sustained rate performance (1003.0 mAh g‒1 at 1675 mA g‒1), and stable cycling (83.5% retention over 450 cycles at 3350 mA g‒1). Moreover, Fe‒N1/S positive electrodes enable sodium | |sulfur pouch cells to deliver a sulfur utilization of 77.4% (1296.9 mAh g‒1) at 0.1 A g‒1. Our work offers a strategy for designing high-activity, fast redox sulfur positive electrodes and validates the practical potential of sodium | |sulfur batteries.