Lithium intercalation and copper extraction in spinel sulfides of general formula Cu(2)MSn(3)S(8)(M=Mn, Fe, Co, Ni)

Cu(2)MSn(3)S(8) (M = Mn, Fe, Co, Ni) and Cu(2-gamma)MSn(3)S(8) (M = Fe, Co) spinel compounds have been studied and used as cathode materials in Li/LiClO4(PC)/spinel sulfide cells. The pristine compounds and electrochemically inserted products have been characterized by X-ray powder diffraction (XRPD) and Sn-119, Fe-57 Mossbauer spectroscopy (MS). Rietveld analysis and Fe-57 MS of the copper extracted phases show that copper extraction takes place from the 8a sites of the spinel structure with oxidisation of the M element. The lithiation process involves a loss of crystallinity and a slight reduction of the host materials. Discharge-charge curves of lithium cells using pristine and deintercalated spinels as cathode materials have been compared. A better performance for the Ni- and Go-containing spinels is observed. After extraction of copper, a significant increase in cell voltage and reversibility is obtained for Co.