LiNi0.5-yMyMn1.5O4 compounds have proven to be of great interest as active cathode material for high-voltage lithium-ion cells. The electrochemical behavior of LiNi0.5-yFeyMn1.5O4 compounds as cathode material in lithium cells is studied here. The charge-discharge curves are characterized by three main plateaus, ascribable to the removal (during charge) or filling (during discharge) of d electrons corresponding to the different redox pairs present: Fe-IV/Fe-III, Ni-IV/Ni-II and Mn-IV/Mn-III. Taking into account the entropy associated to the lithium extraction/insertion and the filling of the different electronic levels, the modelization gives a good reproducibility of the experimental electrochemical curves. The standard potential go of the redox pairs were estimated to be ca. -4.90, -4.80 and -4.23 eV, respectively. (C) 2004 Elsevier Ltd. All rights reserved.