Controllable synthesis of carbon-coated Sn–SnO 2 –carbon-nanoﬁber membrane as advanced binder-free anode for lithium-ion batteries Zhen Shen a,b , Yi Hu a,b,c, *, Yanli Chen a,b , Renzhong Chen a,b , Xia He a,b , Xiangwu Zhang d , Hanfeng Shao a,b , Yan Zhang a,b a Key Laboratory of Advanced Textile Materials and Manufacturing Technology, Ministry of Education, Zhejiang Sci-Tech University, Hangzhou 310018, China b Enineering Research Center for Eco-Dying & Finishing of Textiles, Ministry of Education, Zhejiang Sci-Tech University, Hangzhou 310018, China c Dyeing and ﬁnishing Institute of Zhejiang Sci-Tech University, Zhejiang Sci-Tech Univerisity, Hangzhou 310018, China d Fiber and Polymer Science Program, Department of Textile Engineering, Chemistry and Science, North Carolina State University, Raleigh, NC 27695-8301, USA A R T I C L E I N F O Article history: Received 10 October 2015 Received in revised form 25 November 2015 Accepted 8 December 2015 Available online 10 December 2015 Keywords: Low-temperature hydrothermal method Sucrose Carbon coating Carbon nanoﬁber membrane Lithium-ion batteries A B S T R A C T A carbon-coated composite consisting of Sn, SnO 2 , and porous carbon-nanoﬁber membrane (Sn–SnO 2 – CNF@C) was successfully prepared via electrospinning followed by carbonization and low-temperature hydrothermal treatment. The thickness of the carbon overlayer formed by using sucrose as the carbon source could be well controlled by adjusting the sucrose concentration. The three-dimensional (3D) nanoﬁber network structure allowed the Sn–SnO 2 –CNF@C membrane to be used directly as an anode in lithium-ion batteries without adding any polymer binders or electrical conductors. The composite electrodes of this material exhibited a high discharge capacity of 712.2 mA h g 1 at a high current density of 0.8 A g 1 after 200 cycles, as well as good cycling stability and excellent rate capability, which can be ascribed to the improved electrochemical properties of the Sn–SnO 2 particles provided by the protective carbon coating and the 3D carbon nanoﬁber membrane. The composite can thus be widely used as an advanced binder-free anode material in high-current rechargeable lithium-ion batteries and extended to the fabrication of ﬂexible electrodes. ã 2015 Elsevier Ltd. All rights reserved. 1. Introduction In recent years, lithium-ion batteries (LIBs), which are regarded as one of the predominant power sources for portable devices and hybrid electric vehicles, have attracted increasing attention owing to their superior properties such as high energy density, and long cycle life [1–4]. Although graphite is widely used as an anode material for commercial LIBs because of its stable electrochemical property, the relatively low theoretical capacity (372 mA h g 1 ) greatly limits the development of LIBs with high energy density [5,6]. Accordingly, metals or metal oxides such as Ge, Sn, SnO 2 , Co 3 O 4 , and Mn 3 O 4 have been extensively investigated as anode materials for next-generation LIBs because of their natural abundance and high theoretical capacities [7–12]. Among them, Sn-based materials (metallic Sn, SnO 2 , etc.) have attracted tremendous attention owing to their high theoretical capacities (992, 782 mA h g 1 , respectively), low cost, and non-toxicity [13,14]. However, their large volume changes and severe aggre- gations during the lithium insertion–extraction process lead to electrode pulverization and an unstable solid–electrolyte inter- phase, resulting in rapid capacity fading [15,16]. At present, two substantial strategies are applied collectively to overcome these obstacles. The ﬁrst approach focuses on designing nanocrystalline structures of Sn-based materials with reduced internal strain, high effective electrode–electrolyte contact area, and shortened lithium-diffusion length [2,17–20]. The second strategy exploits ideal matrices used as buffer matrices to restrain the volume expansion and contraction [21–23]. Carbon coatings have been one of the most studied methods because they not only enhance the electronic conductivity of the entire electrode, but also suppress the large volume change as well as alleviate the side reactions at the interface between the active substrate and the electrolyte by preventing them from direct contact with each other [15,24–26], which can enhance the electrochemical performance of Sn-based anode materials in LIBs [27–29]. Among various carbon-coating strategies, the hydrothermal method has attracted * Corresponding author at: 928 Second Avenue, Xiasha Higher Education Zone, Hangzhou 310018, China. Tel.: +86 13588321680. E-mail address: huyi-v@zstu.edu.cn (Y. Hu). http://dx.doi.org/10.1016/j.electacta.2015.12.062 0013-4686/ ã 2015 Elsevier Ltd. All rights reserved. Electrochimica Acta 188 (2016) 661–670 Contents lists available at ScienceDirect Electrochimica Acta journa l home page : www.e lsevier.com/loca te/ele cta cta