| Graphene-based lithium-sulfur batteries Liam Bird1; Kai Xi1; Cheng-yen Lao1; Vasant Kumar1; Andrea Ferrari1; Caterina Ducati1; 1UNIVERSITY OF CAMBRIDGE, Cambridge, United Kingdom; PAPER: 453/Battery/Regular (Oral) SCHEDULED: 17:10/Fri. 25 Oct. 2019/Coralino ABSTRACT: Lithium-sulfur (Li-S) batteries have a theoretical capacity of 1675 mAhg<sup>-1</sup>[1], five times that of conventional Li-ion batteries[2], facilitated by the sulfur cathode undergoing a series of redox reactions to form lithium polysulfides (PS)[3]. However, the continuous diffusion of PS through the electrolyte results in progressive loss of electrical contact to the active material and hence poor capacity retention with repeated cycling[4, 5]. A lightweight, electrically conductive host framework compatible with scalable manufacture is therefore required to exploit sulfur’s low cost and abundance[6] in batteries with sustained high capacity. Templated mesoporous carbons, including CMK-3, are electronically conductive and have a hierarchical porous structure suitable for constraining PS[7]. However, graphene and related materials (GRMs) are compatible with higher throughput manufacturing processes[8]. In addition to high conductivity[8], mechanical strength[8], and surface area, GRMs offer opportunities for tunable functionalisation to increase PS binding energy to the host framework[9]. Here, we investigate the use of graphene nanoplatelets synthesised by microfluidization[10] (GNPs) and graphene oxide (GO) with CMK-3 as composite sulfur hosts for Li-S batteries. We find that a composite of GNPs and CMK-3 improves the capacity of Li-S batteries, and that a composite of GO and CMK-3 improves the capacity retention of batteries for the first ~100 cycles, compared to CMK-3 alone in identical conditions. The incorporation of GNPs appears to enhance the contribution of long-chain PS (Li2Sx for 4≤x≤8) to the cell’s capacity, demonstrating improved constraint of this active material in contact with the conducting host. This improves the cycling capability of Li-S batteries, facilitating their application in electric vehicles and grid-scale renewable energy storage. References: 1 J. R. Akridge, et al. Solid State Ion. 175, 243 (2004) 2 K. Mizushima, et al. Mater. Res. Bull. 15, 783 (1980) 3 E. Peled, J. Electrochem. Soc., 136, 1621 (1989) 4 Y. V. Mikhaylik et al., J Electrochem. Soc. 151, A1969 (2004) 5 S.-E. Cheon, et al., J. Electrochem. Soc. 150, A796 (2003) 6 A. Manthiram, et al., Chem. Rev. 114, 11751 (2014) 7 X. Ji, K. T. Lee, L. F. Nazar, Nat. Mater. 8, 500 (2009) 8 A. C. Ferrari, et al. Nanoscale, 11, 4598 (2015) 9 X. Zhou at al. J. Power Sources 243, 993 (2013) 10 P. G. Karagiannidis et al. ACS Nano 11, 2742 (2017) |
