Engineering Fe-N Coordination Structures for Fast Redox Conversion in Lithium-Sulfur Batteries.
basic_science · Level V
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- Record sourced from PubMed, PMID 34145629.
- Also identified by DOI 10.1002/adma.202100171.
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Abstract
Critical drawbacks, including sluggish redox kinetics and undesirable shuttling of polysulfides (Li<sub>2</sub> S<sub>n</sub> , n = 4-8), seriously deteriorate the electrochemical performance of high-energy-density lithium-sulfur (Li-S) batteries. Herein, these challenges are addressed by constructing an integrated catalyst with dual active sites, where single-atom (SA)-Fe and polar Fe<sub>2</sub> N are co-embedded in nitrogen-doped graphene (SA-Fe/Fe<sub>2</sub> N@NG). The SA-Fe, with plane-symmetric Fe-4N coordination, and Fe<sub>2</sub> N, with triangular pyramidal Fe-3N coordination, in this well-designed configuration exhibit synergistic adsorption of polysulfides and catalytic selectivity for Li<sub>2</sub> S<sub>n</sub> lithiation and Li<sub>2</sub> S delithiation, respectively. These characteristics endow the SA-Fe/Fe<sub>2</sub> N@NG-modified separator with an optimal polysulfides confinement-catalysis ability, thus accelerating the bidirectional liquid-solid conversion (Li<sub>2</sub> S<sub>n</sub> ↔Li<sub>2</sub> S) and suppressing the shuttle effect. Consequently, a Li-S battery based on the SA-Fe/Fe<sub>2</sub> N@NG separator achieves a high capacity retention of 84.1% over 500 cycles at 1 C (pure S cathode, S content: 70 wt%) and a high areal capacity of 5.02 mAh cm<sup>-2</sup> at 0.1 C (SA-Fe/Fe<sub>2</sub> N@NG-supported S cathode, S loading = 5 mg cm<sup>-2</sup> ). It is expected that the outcomes of the present study will facilitate the design of high-efficiency catalysts for long-lasting Li-S batteries.