Nano-composites SnO(VO x ) as anodes for lithium ion batteries

Abstract

Nano-composites of SnO(V 2O 3) x (x=0, 0.25, and 0.5) and SnO(VO) 0.5 are prepared from SnO and V 2O 3/VO by high-energy ball milling (HEB) and are characterized by X-ray diffraction (XRD), scanning electron microscopy, and high-resolution transmission electron microscopy techniques. Interestingly, SnO and SnO(VO) 0.5 are unstable to HEB and disproportionate to Sn and SnO 2, whereas HEB of SnO(V 2O 3) x gives rise to SnO 2.VO x . Galvanostatic cycling of the phases is carried out at 60 mAg -1 (0.12 C) in the voltage range 0.005-0.8 V vs. Li. The nano-SnO(V 2O 3) 0.5 showed a first-charge capacity of 435(±5)mAhg -1 which stabilized to 380(±5)mAhg -1 with no noticeable fading in the range of 10-60 cycles. Under similar cycling conditions, nano-SnO (x=0), nano-SnO(V 2O 3) 0.25, and nano-SnO(VO) 0.5 showed initial reversible capacities between 630 and 390(±5)mAhg -1. Between 10 and 50 cycles, nano-SnO showed a capacity fade as high as 59%, whereas the above two VO x -containing composites showed capacity fade ranging from 10% to 28%. In all the nano-composites, the average discharge potential is 0.2-0.3 V and average charge potential is 0.5-0.6 V vs. Li, and the coulombic efficiency is 96-98% after 10 cycles. The observed galvanostatic cycling, cyclic voltammetry, and ex situ XRD data are interpreted in terms of the alloying-de-alloying reaction of Sn in the nano-composite "Sn-VO x -Li 2O" with VO x acting as an electronically conducting matrix. © 2010 Springer-Verlag.