ORIGINAL PAPER Fe@Ag nanoparticles decorated reduced graphene oxide as ultrahigh capacity anode material for lithium-ion battery Necip Atar 1 & Tanju Eren 1 & Mehmet Lütfi Yola 2 & Hüsnü Gerengi 3 & Shaobin Wang 4 Received: 13 June 2015 /Revised: 9 July 2015 /Accepted: 18 July 2015 /Published online: 30 July 2015 # Springer-Verlag Berlin Heidelberg 2015 Abstract In the present study, we report the synthesis of Fe@Ag nanoparticles/2-aminoethanethiol functionalized re- duced graphene oxide (rGO) composite (Fe@AuNPs- AETrGO) and its application as an improved anode material for lithium-ion batteries (LIBs). The structure of the Fe@AgNPs-AETrGO composite was characterized by trans- mission electron microscopy (TEM), X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray pho- toelectron spectroscopy (XPS). The electrochemical perfor- mance was investigated at different charge/discharge current rates by using CR2032 coin-type cells and cyclic voltammetry (CV). It was found that the spherical Fe@AuNPs were highly dispersed on the rGO sheets. Moreover, the Fe@AuNPs- AETrGO composite showed high specific gravimetric capac- ity of about 1500 mAh g -1 and long-term cycle stability. Keywords Reduced graphene oxide . Metal nanoparticle . Core-shell . Anode . Lithium-ion battery Introduction In recent decades, there have been many reports on energy storage devices with high energy density and long cycle life [1]. Lithium-ion batteries (LIBs) have been applied as an im- portant power source owing to their high operating voltage and high energy density [2]. LIBs enable to improve the en- ergy and power density for different kinds of application such as portable electronic devices, power tools, and electric vehi- cles [3–5]. Currently, the fossil fuel has been used for high energy consumption [6]. The LIBs are one of the most impor- tant energy storage systems from renewable sources [7–9]. For these applications, LIBs must possess higher electrical/ ionic conductivity, cycling stability, rate capability, and low cost. The performance of LIBs depends on the cathode and an- ode materials. In this respect, the use of carbon-based anode materials [10], containing carbon fibers [11], carbon nano- tubes [12], and graphene [8, 13], could benefit the LIBs in terms of specific capacity and cycle stability [14]. Different investigations on graphene and reduced graphene oxide (rGO) for electrochemical energy storage [8], electronics [15], and biosensors applications [16] have been reported. Furthermore, rGO has been proposed as a potential electrode material for LIBs because of its chemical structure [8], flexibility [17], high surface area [18], and electrical conductivity [19]. More- over, different investigations on nanoparticle-based nanocom- posites for electrochemical energy storage, biosensors, and electronics applications have been reported [20–28]. There are some composites based on carbon materials functionalized by nanoparticles such as Si and Au. In addition, Fe 3 O 4 [29–31] was used as an anode material [32, 33] to increase the performance of LIBs. The bimetallic core@shell nanopar- ticles can be well controlled and their morphologies show important physicochemical properties [34, 35], which has * Necip Atar necipatar@gmail.com * Shaobin Wang shaobin.wang@curtin.edu.au 1 Department of Chemical Engineering, Pamukkale University, Denizli, Turkey 2 Department of Metallurgical and Materials Engineering, Sinop University, Sinop, Turkey 3 Corrosion Research Laboratory, Kaynasli Vocational College, Duzce University, Kaynasli, Duzce 81900, Turkey 4 Department of Chemical Engineering, Curtin University, GPO Box U1987, Perth, WA 6845, Australia Ionics (2015) 21:3185–3192 DOI 10.1007/s11581-015-1520-1