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Title: Sulfur encapsulation by MOF-derived CoS 2 embedded in carbon hosts for high-performance Li–S batteries
Li–S batteries have attracted great attention for their combined advantages of potentially high energy density and low cost. To tackle the capacity fade from polysulfide dissolution, we have developed a confinement approach by in situ encapsulating sulfur with a MOF-derived CoS 2 in a carbon framework (S/Z-CoS 2 ), which in turn was derived from a sulfur/ZIF-67 composite (S/ZIF-67) via heat treatment. The formation of CoS 2 was confirmed by X-ray absorption spectroscopy (XAS) and its microstructure and chemical composition were examined through cryogenic scanning/transmission electron microscopy (Cryo-S/TEM) imaging with energy dispersive spectroscopy (EDX). Quantitative EDX suggests that sulfur resides inside the cages, rather than externally. S/hollow ZIF-67-derived CoS 2 (S/H-CoS 2 ) was rationally designed to serve as a control material to explore the efficiency of such hollow structures. Cryo-STEM-EDX mapping indicates that the majority of sulfur in S/H-CoS 2 stays outside of the host, despite its high void volumetric fraction of ∼85%. The S/Z-CoS 2 composite exhibited highly improved battery performance, when compared to both S/ZIF-67 and S/H-CoS 2 , due to both the efficient physical confinement of sulfur inside the host and strong chemical interactions between CoS 2 and sulfur/polysulfides. Electrochemical kinetics investigations revealed that the CoS 2 could serve as an electrocatalyst to accelerate the redox reactions. The composite could provide an areal capacity of 2.2 mA h cm −2 after 150 cycles at 0.2C and 1.5 mA h cm −2 at 1C. This novel material provides valuable insights for further development of high-energy, high-rate and long-life Li–S batteries.  more » « less
Award ID(s):
1719875
PAR ID:
10149165
Author(s) / Creator(s):
; ; ; ; ; ;
Date Published:
Journal Name:
Journal of Materials Chemistry A
Volume:
7
Issue:
37
ISSN:
2050-7488
Page Range / eLocation ID:
21128 to 21139
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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