In Situ 119Sn Mössbauer Effect Study of the Reaction of Lithium with Si Using a Sn Probe

Abstract

The reaction of lithium with amorphous Si was studied by Mössbauer effect spectroscopy using small amounts of Sn as probe atoms. Two powder samples, amorphous- and amorphous-, were prepared by magnetron sputtering and investigated using in situ and ex situ Mössbauer spectroscopy. There are two gently sloping plateaus in the voltage vs capacity of cells whose origin has never been explained. There is a clear step between these plateaus at Li atoms per Si atom, or . The step between the plateaus is found to correlate with dramatic changes in the Mössbauer effect spectra with in at , which suggest the step occurs at the point when each Si atom is surrounded only by Li atom first neighbors. The changes in the Mössbauer spectra during the delithiation of the cells also give clues about electrode failure mechanisms.