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

摘要

The use of ~(57)Fe as a local Moessbauer 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 Li_4Ti_5O_(12) to obtain Fe substituted spinel and Li_2Ti_3O_7 ramsdellite. In the case of Li_4Ti_5O_(12) iron ions are reduced (Fe~Ⅲ → Fe~Ⅱ), then migrate from tetrahedral to octahedral sites allowing us to establish the spinel reversible rocksalt phase transition. Such phase transition definitively explains the well-defined plateau observed in the electrochemical potential curves. In the case of Li_2Ti_3O_7 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.