Mossbauer spectra as a "fingerprint" in tin-lithium compounds: Applications to Li-ion batteries

Several Li-Sn crystalline phases, i.e. Li2Sn5, LiSn, Li7Sn3, Li5Sn2, Li13Sn5, Li7Sn2 and Li22Sn5 were prepared by ball-milling and characterized by X-ray powder diffraction and Sn-119 Mossbauer spectroscopy. The analysis of the Mossbauer hyperfine parameters, i.e. isomer shift (delta) and quadrupole splitting (Delta), made it possible to define two types of Li-Sn compounds: the Sn-richest compounds (Li2Sn5, LiSn) and the Li-richest compounds (Li7Sn3, Li5Sn2, L13Sn5, Li7Sn2, Li22Sn5). The isomer shift values ranged from 2.56 to 2.38 mms(-1) for Li2Sn5, LiSn and from 2.07 to 1.83 mms(-1) for Li7Sn3, Li5Sn2, Li13Sn5, Li7Sn2 and Li22Sn5, respectively. A Delta-delta correlation diagram is introduced in order to identify the different phases observed during the electrochemical process of new Sn-based materials. This approach is illustrated by the identification of the phases obtained at the end of the first discharge of eta-Cu6Sn5 and SnB0.6P0.4O2.9. (c) 2006 Elsevier Inc. All rights reserved.