In Situ Synthesis of Bipyramidal Sulfur with 3D Carbon Nanotube Framework for Lithium-Sulfur Batteries

A one‐pot synthesis of three‐dimensional carbon nanotube frameworks with bipyramidal sulfur particles and the application of these materials for a cathode in lithium–sulfur (Li–S) battery are reported. By simple mixing of multi‐walled carbon nanotubes (MWCNTs), sulfur powder, and capping agents in w...

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Bibliographic Details
Published in:Advanced functional materials 2014-04, Vol.24 (15), p.2248-2252
Main Authors: Wang, Lina, Zhao, Yu, Thomas, Morgan L., Byon, Hye Ryung
Format: Article
Language:English
Subjects:
Additives
bipyramidal sulfur
Carbon nanotubes
Cathodes
Conduction
Electrolytic cells
ionic liquids
lithium-sulfur battery
Sulfur
Synthesis
Three dimensional
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Summary:A one‐pot synthesis of three‐dimensional carbon nanotube frameworks with bipyramidal sulfur particles and the application of these materials for a cathode in lithium–sulfur (Li–S) battery are reported. By simple mixing of multi‐walled carbon nanotubes (MWCNTs), sulfur powder, and capping agents in water/tetrahydrofuran, micrometer bipyramidal sulfur particles enclosed with MWCNTs are synthesized. The MWCNTs spontaneously form a 3D conducting network inside and outside the sulfur particle. Along the edge of MWCNT framework, a sulfur particle‐free region is present, which comprises ≈35 vol% based on the total volume. These sulfur‐MWCNT bipyramidal particles are mixed with conductive carbon additive to prepare binder‐free cathode for Li–S cells. The Li–S cells deliver a specific discharge capacity of ≈1600 mAh g−1 at 0.05 C on the first cycle. In particular, these Li–S cells show high rate stability and Coulombic efficiency with deep discharge and charge (1.0–3.0 V vs Li/Li+). This resultant performance can arise from 1) homogeneous distribution of the conducting MWCNT framework and the carbon additive coating layer on the sulfur particle, which allow rapid Li+ ion/electrolyte diffusion and mitigation of polysulfide shuttle, respectively, and 2) the sulfur‐free buffer space accommodating volume expansion. It is expected that this new cathode design with the simple synthetic process can reduce the number of preparation steps, thus allowing the construction of a low‐cost Li–S battery. 3D carbon nanotube frameworks with bipyramidal sulfur particles are formed via a one‐pot synthesis. The conducting frameworks enclosing both sulfur and sulfur‐free regions maintain high electronic conductivity. Additional coating of the framework using conductive additives aids in mitigating the polysulfide shuttle. These structures, employed in cathodes for Li–S batteries, provide high rate stability and reversibility during deep 100 cycles.
ISSN:1616-301X
1616-3028
DOI:10.1002/adfm.201302915