LiNi0.5−y M y Mn1.5O4 compounds have proven to be of great interest as active cathode material for high-voltage lithium-ion cells. The electrochemical behavior of LiNi0.5−y Fe y Mn1.5O4 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: FeIV/FeIII, NiIV/NiII and MnIV/MnIII. 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 μ 0 of the redox pairs were estimated to be ca. −4.90, −4.80 and −4.23eV, respectively.