Electrochemical Properties of Ti-Ni-Sn Materials Predicted by 119sn Mössbauer Spectroscopy

The electrochemical activity of TiNiSn, TiNi 2Sn and Ti 6Sn 5 compounds considered as negative electrode materials for Li-ion batteries has been predicted from the isomer shift- Hume-Rothery electronic density correlation diagram. The ternary compounds were obtained from solid-state reactions and Ti 6Sn 5 by ball milling. The 119Sn Mössbauer parameters were experimentally determined and used to evaluate the Hume-Rothery electronic density [e av]. The values of [e av] are in the region of Li-rich Li-Sn alloys for Ti 6Sn 5 and outside this region for the ternary compounds, suggesting that the former compound is electrochemically active but not the two latter ones. Electrochemical tests were performed for these different materials confirming this prediction. The close values of [e av] for Ti 6Sn 5 and Li-rich Li-Sn alloys indicate that the observed good capacity retention could be related to small changes in the global structures during cycling.