Confined Lithium–Sulfur Reactions in Narrow-Diameter Carbon Nanotubes Reveal Enhanced Electrochemical Reactivity

We demonstrate an unusual electrochemical reaction of sulfur with lithium upon encapsulation in narrow-diameter (subnanometer) single-walled carbon nanotubes (SWNTs). Our study provides mechanistic insight on the synergistic effects of sulfur confinement and Li+ ion solvation properties that culmina...

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Bibliographic Details
Published in:ACS nano 2018-10, Vol.12 (10), p.9775-9784
Main Authors: Fu, Chengyin, Oviedo, M. Belén, Zhu, Yihan, von Wald Cresce, Arthur, Xu, Kang, Li, Guanghui, Itkis, Mikhail E, Haddon, Robert C, Chi, Miaofang, Han, Yu, Wong, Bryan M, Guo, Juchen
Format: Article
Language:English
Subjects:
controlled solid-state reactions
electrochemical systems
ENERGY STORAGE
lithium-sulfur battery
single-walled carbon nanotubes
sub-nanoscale confined sulfur
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Summary:We demonstrate an unusual electrochemical reaction of sulfur with lithium upon encapsulation in narrow-diameter (subnanometer) single-walled carbon nanotubes (SWNTs). Our study provides mechanistic insight on the synergistic effects of sulfur confinement and Li+ ion solvation properties that culminate in a new mechanism of these sub-nanoscale-enabled reactions (which cannot be solely attributed to the lithiation–delithiation of conventional sulfur). Two types of SWNTs with distinct diameters, produced by electric arc (EA-SWNTs, average diameter 1.55 nm) or high-pressure carbon monoxide (HiPco-SWNTs, average diameter 1.0 nm), are investigated with two comparable electrolyte systems based on tetraethylene glycol dimethyl ether (TEGDME) and 1,4,7,10,13-pentaoxacyclopentadecane (15-crown-5). Electrochemical analyses indicate that a conventional solution-phase Li–S reaction occurs in EA-SWNTs, which can be attributed to the smaller solvated [Li­(TEGDME)]+ and [Li­(15-crown-5)]+ ions within the EA-SWNT diameter. In stark contrast, the Li–S confined in narrower diameter HiPco-SWNTs exhibits unusual electrochemical behavior that can be attributed to a solid-state reaction enabled by the smaller HiPco-SWNT diameter compared to the size of solvated Li+ ions. Our results of the electrochemical analyses are corroborated and supported with various spectroscopic analyses including operando Raman, X-ray photoelectron spectroscopy, and first-principles calculations from density functional theory. Taken together, our findings demonstrate that the controlled solid-state lithiation–delithiation of sulfur and an enhanced electrochemical reactivity can be achieved by sub-nanoscale encapsulation and one-dimensional confinement in narrow-diameter SWNTs.
ISSN:1936-0851
1936-086X
DOI:10.1021/acsnano.7b08778