Accelerating Sulfur Redox Chemistry by Atomically Dispersed Zn-N4 Sites Coupled with Pyridine-N Defects on Porous Carbon Sheets.
Small
; 20(2): e2305508, 2024 Jan.
Article
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| MEDLINE
| ID: mdl-37670540
ABSTRACT
Single-atom catalysts (SACs) with specific N-coordinated configurations immobilized on the carbon substrates have recently been verified to effectively alleviate the shuttle effect of lithium polysulfides (LiPSs) in lithium-sulfur (LiâS) batteries. Herein, a versatile molten salt (KCl/ZnCl2 )-mediated pyrolysis strategy is demonstrated to fabricate Zn SACs composed of well-defined Zn-N4 sites embedded into porous carbon sheets with rich pyridine-N defects (ZnâN/CS). The electrochemical kinetic analysis and theoretical calculations reveal the critical roles of Zn-N4 active sites and surrounding pyridine-N defects in enhancing adsorption toward LiPS intermediates and catalyzing their liquid-solid conversion. It is confirmed by reducing the overpotential of the rate-determining step of Li2 S2 to Li2 S and the energy barrier for Li2 S decomposition, thus the ZnâN/CS guarantees fast redox kinetics between LiPSs and Li2 S products. As a proof of concept demonstration, the assembled LiâS batteries with the ZnâN/CS-based sulfur cathode deliver a high specific capacity of 1132 mAh g-1 at 0.1 C and remarkable capacity retention of 72.2% over 800 cycles at 2 C. Furthermore, a considerable areal capacity of 6.14 mAh cm-2 at 0.2 C can still be released with a high sulfur loading of 7.0 mg cm-2 , highlighting the practical applications of the as-obtained ZnâN/CS cathode in LiâS batteries.
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2024
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