Inhibition on polysulfides dissolve during the discharge-charge by using fish-scale-based porous carbon for lithium-sulfur battery Mengyao Gao a , Chengming Li a , Naiqiang Liu a , Yilei Chen a , Weikun Wang b , Hao Zhang b , Zhongbao Yu b , Yaqin Huang a, * a State Key Laboratory of Chemical Resource Engineering, The Key Laboratory of Beijing City on Preparation and Processing of Novel Polymer Materials, Beijing University of Chemical Technology, 15 Beisanhuan East Road, Beijing 100029, PR China b Research Institute of Chemical Defense, 35 Huayuan North Road, Beijing 100191, PR China A R T I C L E I N F O Article history: Received 20 June 2014 Received in revised form 16 October 2014 Accepted 23 October 2014 Available online 27 October 2014 Keywords: Lithium-sulfur battery Polysulfides Asymmetry electrode Porous coating layer A B S T R A C T The fish scale derived hierarchical porous carbon has been studied as an inhibitor to capture the polysulfides for lithium-sulfur battery by ex situ ultraviolet-visible absorption spectroscopy and SEM analysis. The results showed that the capacity retention of the cathode with porous carbon as additive increased from 44% to 59% after 50 cycles at 0.1 C compared with the common cathode. Attracted on the excellent performance of cathode with porous carbon, the asymmetry electrode was fabricated by coating a porous layer on the cathode to trap the polysulfides produced during the discharge-charge process further. The initial discharge specific capacity is 1426 mAhg 1 with a capacity retention of 81% after 50 cycles at 1 C, and retains a reversible capacity of 990 mAhg 1 after 100 cycles with coulombic efficiency above 98%. ã 2014 Elsevier Ltd. All rights reserved. 1. Introduction To meet the requirements of energy storage system employed in electric vehicles, smart energy grids and renewable energies, sustainable development of next-generation battery is becoming a challengeable task for researchers [1]. In this regard, state-of-the- art lithium-sulfur battery based on redox couple is becoming more and more popular due to the high theoretical specific capacity of 1675 mAhg 1 and theoretical specific energy of 2600 Wh kg 1 , assuming the complete reaction of lithium with sulfur to form Li 2 S [2–5]. In addition, elemental sulfur also has advantages of non- toxic, naturally abundant, and environmentally benign [6]. To achieve the commercialization of lithium-sulfur battery, the following challenges must be solved: 1) low utilization of active materials; 2) low coulombic efficiency and severe capacity fading. This is mainly caused by the soluble polysulfides produced during the electrochemistry process gradually dissolving into the electrolyte. At the same time, long chain polysulfides that formed as reaction intermediates dissolve into the electrolyte, and then migrate to the Li anode where it reacts with Li in a parasitic fashion to generate shorter chain polysulfides. The shorter chain poly- sulfides diffuse back to the sulfur cathode and regenerate the long chain polysulfides. This process takes place repeatedly, creating an internal shuttling mechanism during the electrochemical reaction [7,8]. Recently, multiple strategies have been employed to restrain the intermediate lithium polysulfides dissolve into the electrolyte and increase the sulfur utilization of the lithium-sulfur battery. Employing porous materials as internal reservoirs which can restrain polysulfides dissolution and shuttling during electro- chemical reaction [9], applying surface coatings of conductive polymers [10] have been found promising ways to improve the discharge capacity and the cycle life of lithium-sulfur battery. The polysulfide shuttle was tuned by the loading of sulfur and electrolyte [11]. Small sulfur molecules have been synthesised in a confined microporous carbon shell [12], a S-TiO 2 yolk-shell nanostructure with improved cycling stability was reported for it had sufficient free space to accommodate the volume expansion of sulfur [13]. A carbon membrane was placed to act as a physical barrier to block the polysulfide species [14,15], a carbonized leaf composed of a natural abundant plant material as a polysulfide diffusion inhibitor has been carried out [16]. And a charge operation control that offers tremendous improvement with various lithium-sulfur battery systems was measured to recharge lithium-sulfur cells [17]. However, achieving high capacity retention with minimum capacity loss for lithium-sulfur battery still faces a significant challenge [18]. This is mainly due to the big gap between battery materials efforts and fundamental research * Corresponding author. Tel: +86 10 6443 8266; fax: +86 10 6443 8266. E-mail address: huangyaqin9@gmail.com (Y. Huang). http://dx.doi.org/10.1016/j.electacta.2014.10.118 0013-4686/ ã 2014 Elsevier Ltd. All rights reserved. Electrochimica Acta 149 (2014) 258–263 Contents lists available at ScienceDirect Electrochimica Acta journal homepa ge: www.elsev ier.com/locate/electacta