Issue 36, 2015

Fabrication of functionalized polysulfide reservoirs from large graphene sheets to improve the electrochemical performance of lithium–sulfur batteries

Abstract

The effect of graphene lateral size on the electrochemical performance of lithium–sulfur (Li–S) batteries is often ignored. In this study, the thermally exfoliated large lateral-sized graphene (denoted LTG) was employed as the conductive matrix to support sulfur, and its performance was then compared with that of a smaller lateral-sized graphene (denoted STG) for Li–S batteries. The results showed that the LTG–S composite exhibited much higher capacity retention (53%) versus the STG–S (29%) and better rate capabilities. Because they were both identical in morphology, in terms of sulfur content and sulfur distribution, the improved properties probably resulted from the potential prevention of polysulfide diffusion upon cycling due to the larger graphene-based network and higher aspect ratio of the LTG matrix, referred as better polysulfide reservoirs. To further improve the cell performance, a reduced graphene oxide-coated carbon fiber paper (RCF) was inserted between the LTG–S cathode and the separator by a simple drop-coat method, which provided an increased conductive surface area for polysulfides to be oxidized/reduced and buffered volume expansion. As expected, the discharge capacities of 1143 and 622 mA h g−1 at first use and after 100th cycles were obtained with an average Coulombic efficiency of 99.7%, which were higher than 847 and 455 mA h g−1 for the cathode without the RCF, respectively. This study highlights the significance of large graphene sheets and interlayers on the inhibition of polysulfide diffusion and offers a new way to solve the problems of Li–S batteries.

Graphical abstract: Fabrication of functionalized polysulfide reservoirs from large graphene sheets to improve the electrochemical performance of lithium–sulfur batteries

Supplementary files

Article information

Article type
Paper
Submitted
30 Apr 2015
Accepted
05 Aug 2015
First published
06 Aug 2015

Phys. Chem. Chem. Phys., 2015,17, 23481-23488

Fabrication of functionalized polysulfide reservoirs from large graphene sheets to improve the electrochemical performance of lithium–sulfur batteries

C. Fan, H. Li, L. Zhang, H. Sun, X. Wu, H. Xie and J. Zhang, Phys. Chem. Chem. Phys., 2015, 17, 23481 DOI: 10.1039/C5CP02531A

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