119Sn Mossbauer spectroscopy study of the mechanism of lithium reaction with self-organized Ti1/2Sn1/2O2 nanotubes

Novel self-organized Ti1/2Sn1/2O2 nanotubes can be produced by the electrochemical anodization of co-sputtered Ti-Sn thin-films. Combined X-ray photoelectron spectroscopy and Sn-119 Mossbauer spectroscopy of pristine samples evidenced the octahedral substitution of Sn4+ for Ti4+ in the TiO2 structure. In addition to the improved lithium storage behaviour of the Ti1/2Sn1/2O2 nanotubes, ex situ Sn-119 Mossbauer spectroscopy of cycled electrodes has sufficiently confirmed that no decomposition of the Ti1/2Sn1/2O2 structure occurred, and that no Li-Sn phase was formed during the discharge, corroborating that the electrochemical reaction is due exclusively to Li+ insertion into the Ti1/2Sn1/2O2 nanotubes in the 1 <= U/V <= 2.6 voltage range.