Pierre Kubiak

Mössbauer Spectrometry as a Powerful Tool to Study Lithium Reactivity Mechanisms for Battery Electrode Materials

The use of 57Fe as a local Mossbauer probe is of high interest for studying mechanisms induced by lithium insertion. In this way the substitutions Ti/Fe and Li/Fe have been carried out for Li4Ti5O12 to obtain Fe substituted spinel and Li2Ti3O7 ramsdellite. In the case of Li4Ti5O12 iron ions are reduced (FeIII → FeII), then migrate from tetrahedral to octahedral sites allowing us to establish the spinel ↔ rocksalt phase transition. Such phase transition definitively explains the well-defined plateau observed in the electrochemical potential curves. In the case of Li2Ti3O7 ramsdellite, all the iron ions are located on octahedral sites and the quadrupole splittings are related to the number of lithium in the neighbourhood of probed atoms.