Analytical characterization by X-ray photoelectron spectroscopy of quaternary chalcogenides for cathodes in lithium cells

Abstract

Cdln₂S₂Se₂ cathodes, discharged in a lithium cell at significant points of the discharge curve, have been analysed by X-ray photoelectron spectroscopy (XPS) and information on the surface chemical composition has been used to obtain a deeper knowledge of the cell discharge mechanism.

XPS characterization indicated that, with an initial discharge greater than 0.3 F, the cathode surface chemistry was heavily modified, owing mainly to a topotactic reaction of electrolyte anions at the interface and, to a lesser extent, to the intercalation (and reduction) of electrolyte anions into the layered structure of the chalcogenide.

On the basis of thermodynamic considerations the formation of species identified by XPS on the discharged cathodes has been tentatively explained and the results seem to reinforce the general model obtained by a previous electrochemical and X-ray diffraction investigation.