Brush-structured sulfur-polyaniline-graphene composite as cathodes for lithium-sulfur batteries
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Research Letter
Brush-structured sulfur–polyaniline–graphene composite as cathodes for lithium–sulfur batteries Heguang Liu , Ruixuan Jing, and Caiyin You, School of Materials Science and Engineering, Xi’an University of Technology, Xi’an 710048, China Qifeng Zhong, Department of Pharmaceutical Equipment and Electronic Instruments, School of Engineering, China Pharmaceutical University, Nanjing 210009, China Address all correspondence to Qifeng Zhong at [email protected] (Received 28 August 2019; accepted 29 October 2019)
Abstract In this work, the authors report a facile method for the preparation of brush-structured nanocomposites of sulfur–polyaniline–graphene oxide (S–PANI–G) that were used for cathode materials of lithium–sulfur batteries (LSBs). The morphology and structure of composite were studied by x-ray photoelectron microscopy, transmission electron microscopy, scanning electron microscopy, and x-ray diffraction analysis. The nanocomposites exhibited good electrochemical performance involving good rate performance, high capacity, and promising cycling stability. The good performance of S–PANI–G results from the synergistic effect of sulfur, polyaniline, and graphene oxide. The composite and method reported here pave the way for the design and synthesis of novel cathode materials for LSBs.
Introduction Lithium–sulfur batteries (LSBs) with extremely high energy density (2567 Wh/kg) and theoretical capacity (1672 mAh/g) have attracted numerous attention as a promising energy storage technology.[1–3] Compared to conventional rechargeable batteries, LSBs have almost five times higher energy density thanks to the complete reaction of lithium with sulfur forming Li2S.[4–8] Nevertheless, LSBs are plagued with some problems that hinder their wide practical application. The first problem is that the sulfur is electrically insulating (5 × 10−28 S/m), and its final discharge product of Li2S leads to poor electrochemical reaction kinetics, resulting in low active material utilization.[9,10] And the other problem needs to be solved is the large volume variation (approximately 80%) of sulfur during the discharge and charge processes, which naturally leads to the pulverization of active materials and severe capacity fading.[11] Moreover, diffusion of highly soluble polysulfide intermediates can also induce the sulfur shuttle mechanism and result in the irreversible changes of physicochemical properties of the electrolyte.[12,13] The negative effects of the poor electrochemical reaction kinetics problems could be effectively reduced by combining with the conducting materials, such as graphene,[14,15] carbon nanotubes,[16] conducting polymers,[17,18] and other carbon matrixes,[19–27] forming the composites. As referred to the improvement of the cycling life of the LSBs, electrolyte additives, such as LiNO3, have been demonstrated to reduce the capacity decay because the additives enhance polysulfide stability in the electrolyte, they protect the anode of lithium foil from electrochemically and chemically reaction, and they
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