TIME-DEPENDENT LITHIUM INSERTION IN MIXED-VALENCE TIN, INDIUM SULFIDE SPINELS - TIN MOSSBAUER-SPECTROSCOPY AND LITHIUM NMR

Solid state lithium batteries are very promising power sources. However, many problems concerning lithium insertion/extraction are yet to be resolved. Tin-indium mixed valence sulfides with spinel structure have been used as lithium insertion host-matrix. The chemical way via n-butyllithium has been chosen for its softness. Atomic emission spectroscopy reveals the time dependence of the reaction. X-ray diffraction shows that the reaction is topotactic. An electronic transfer Sn(IV) reversible Sn(II) is evident from S-119 n Mossbauer spectra. The knowledge of the Lamb-Mossbauer factors of Sn(IV) and Sn(II) allows the evaluation of the Sn(IV) quantity reduced further to lithium insertion and then, the amount of lithium taking part in this process. The results lead us to the inclusion of a second oxidoreduction mechanism In(III) reversible InI. Li-7 N.M.R. analysis reveals a double-line subspectra related to two types of lithium with different mobilities.