Novel Li 4 Ti 5 O 12 /Sn nano-composites as anode material for lithium ion batteries Arumugam Sivashanmugam a, *, Sukumaran Gopukumar a , Ramasamy Thirunakaran a , Chandrasekaran Nithya a , Shanmuga Prema b a Central Electrochemical Research Institute (Council of Scientific and Industrial Research), Karaikudi 630 006, Tamil Nadu, India b Department of Chemistry, Fatima College, Madurai, Tamil Nadu, India 1. Introduction Of late, Li 4 Ti 5 O 12 has been demonstrated as a prospective negative electrode for lithium-ion batteries [1–3]. It possesses good lithium-ion intercalation and deintercalation capability during charge–discharge cycling and exhibits excellent lithium ion mobility within its structure and therefore stands as promising preposition for high rate battery applications [4–8]. Li 4 Ti 5 O 12 has a spinel related structure (Fd3m space group), and reversible Li + ion insertion into the crystallographic structure occurs at 1.55 V vs. Li/ Li + . Li + ions occupy 8a sites and 1/6th of 16d octahedral sites. Ti 4+ ions occupy the remaining 16d sites and all the 32e sites are occupied by O  atoms. The framework of Li 4 Ti 5 O 12 is very robust. Therefore, insertion and extraction of lithium are extremely reversible [9]. Further, it is a zero-strain material as it undergoes very low volume change during cycling [10]. Every formula unit of Li 4 Ti 5 O 12 can accommodate three lithium ions, so its theoretical capacity is 175 mAh g 1 [11]. However, the low conductivity of Li 4 Ti 5 O 12 (10 9 S cm 1 ) does lead to initial capacity loss and poor rate capability [12], which essentially hinders its commercial worthiness. Many research groups have been, therefore, focusing on enhancing its electronic conductivity in order to obtain sustainable electrochemical performance. Conductive fillers are routinely added to the electrodes to construct conductive percolation network [13–15]. The conductive network is essential to compen- sate the low electronic conductivity of the electrode active materials and to achieve full capacity utilization. Carbon coated Li 4 Ti 5 O 12 by different routes have been studied extensively [16– 19]. On the other hand, tin based alloying anodes have also been envisaged as an alternate anode material for lithium-ion batteries owing to its high specific capacity of 994 mAh g 1 [20–22]. Sn can reversibly form a series of alloys with lithium up to a stoichiometry of Li 4.4 Sn [23]. However, the alloying–dealloying reactions are accompanied by large volume change, which induces mechanical strain resulting in crumbling of active components upon repeated cycling. Therefore, several studies have been reported towards modifying the microstructure and texture of Sn-based material to either by adopting different synthesis routes [24–28] or by making composites [29–32] to provide a facile host structure to buffer the associated expansion during the alloying/de-alloying process. In this article, an attempt has been made to unify the mixed advantages of the two materials and to emerge with a novel Li 4 Ti 5 O 12 /Sn nano composite anode for a practical lithium-ion battery. A comparison of performance of these energy storage Materials Research Bulletin 46 (2011) 492–500 ARTICLE INFO Article history: Received 28 June 2010 Received in revised form 18 November 2010 Accepted 10 January 2011 Available online 16 January 2011 Keywords: Composites X-ray diffraction (XRD) ABSTRACT Li 4 Ti 5 O 12 /Sn nano-composites have been prepared as anode material for lithium ion batteries by high- energy mechanical milling method. Structure of the samples has been characterized by X-ray diffraction (XRD), which reveals the formation of phase-pure materials. Scanning electron microscope (SEM) and transmission electron microscope (TEM) suggests that the primary particles are around 100 nm size. The local environment of the metal cations is confirmed by Fourier transform infrared (FT-IR) and the X-ray photoelectron spectroscopy (XPS) confirms that titanium is present in Ti 4+ state. The electrochemical properties have been evaluated by galvanostatic charge/discharge studies. Li 4 Ti 5 O 12 /Sn–10% composite delivers stable and enhanced discharge capacity of 200 mAh g 1 indicates that the electrochemical performance of Li 4 Ti 5 O 12 /Sn nano-composites is associated with the size and distribution of the Sn particles in the Li 4 Ti 5 O 12 matrix. The smaller the size and more homogeneous dispersion of Sn particles in the Li 4 Ti 5 O 12 matrix exhibits better cycling performance of Li 4 Ti 5 O 12 /Sn composites as compared to bare Li 4 Ti 5 O 12 and Sn particles. Further, Li 4 Ti 5 O 12 provides a facile microstructure to fairly accommodate the volume expansion during the alloying and dealloying of Sn with lithium. ß 2011 Elsevier Ltd. All rights reserved. * Corresponding author. Tel.: +91 4565 227550x357; fax: +91 4565 227779. E-mail address: sivashanmugam@ymail.com (A. Sivashanmugam). Contents lists available at ScienceDirect Materials Research Bulletin journal homepage: www.elsevier.com/locate/matresbu 0025-5408/$ – see front matter ß 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.materresbull.2011.01.007