Combined 57Fe Mössbauer and X-ray diffraction (Rietveld analysis) studies were made of a spinel, before and after chemical Li insertion. In order to accommodate the newly inserted cations, 2 mechanisms operated. Firstly, at low Li contents, cation migration took place from the usually occupied 8a and 16d sites towards the usually unoccupied 8b and 16c sites; with distortion of the S coordination polyhedra. Secondly, at high Li contents, when both 16c and 16d octahedral sites were occupied, a decrease in the distortion of the polyhedra was observed. During insertion, no clear reduction in Fe atoms was observed but there was an increase in the covalent character of the Fe-S bonds.

C.Bousquet, A.Krämer, C.P.Vicente, J.L.Tirado, J.Olivier-Fourcade, J.C.Jumas: Journal of Solid State Chemistry, 1997, 134[2], 238-47