Nb2O5 anchored-Graphene Hybrid Nanocomposites As High Performance Anode for Lithium Ion Batteries

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With the ever-increasing demand for energy storage, lithium ion battery has been an attractive technology, which has revolutionized the portable electronic industry and has recently become popular in the electric vehicle market, due to their superior energy density [1]. Innovative materials chemistry has been the key to various advancements in lithium rechargeable battery [2]. Various transition metal oxides have been widely studied as electrode materials for rechargeable lithium-ion batteries because of their high theoretical capacity, safety, environmental benignity and low cost [3]. Recently, there is great interest in developing graphene-based nanocomposites as high performance electrodes, owing to the multifunctional attributes of such electrodes [4]. Such materials designs are expected to offer marked improvements in energy and power densities. Here, we present the synthesis of Nb2O5 anchored graphene hybrid nanocomposites through simple hydrothermal method and their application as high performance anodes for lithium ion battery. Self-supported nanostructured electrode with graphene as support and with homogenously anchored Nb2O5 nanoparticles has been obtained as shown in Figure 1a. Nanostructured hybrid electrodes have been characterized by X-ray diffraction (XRD), Scanning and Transmission Electron Microscopy (SEM/TEM). Cyclic voltammetry and Galvanostatic charge-discharge cycling measurements have been performed using hybrid nanocomposites as positive electrodes in 1 M LiPF6 –EC/DMC electrolyte vs.Li metal negative electrodes. Electrochemical studies of these hybrid electrodes show improved reversible capacities and power capabilities.Conducting graphene sheets improves the kinetics of the lithium ion and electron transport, and conductivity of the metal oxide by the enhanced particle-particle contact and buffering action during lithiation. Synergistic effect of both Nb2O5 nanocrystals anchored onto conducting graphene layers showed reversible capacity of 192 mAhg-1 up to 50 cycles with C/10 rate, indicating two electron transfer process in LixNb2O5 (Figure 1b). Nb2O5anchored graphene sheets with superior electrochemical performance of high reversible capacity, enhanced rate capability, including an improved electronic and ionic conductivity, can be ideal anodes for high performance lithium ion battery. Figure1: (a) TEM image of Nb2O5-anchored graphene nanocomposites; (b) Charge-discharge galvanostatic curves for Nb2O5-anchored graphene electrtodes cycled at a rate of C/10 versus Li and using a charge cut off voltage of 1 V. References J. -M. Tarascon, M. Armand, Nature, 414 (2001), 359.P. G. Bruce, B. Scrosati, J. -M. Tarascon, Angewandte Chemie International Edition, 47, (2008), 2930.P. Poizot, S. Laruelle, S. Grugeon, L. Dupont & J-M. Tarascon, Nature 407, (2000), 496.Z.-S. Wu, W. Ren, L. Xu, F. Li, H.-M. Cheng, ACS Nano 5, (2011), 5463.