Electrical conductivity and thermoelectric power measurements accompanied by differential scanning calorimetry and X-ray diffraction studies of series of manganese spinel samples with manganese substituted with 3d metals LiMxMn2−xO4 (M = Cr, Fe, Co, Ni, and Cu; x = 0–0.5) were presented. Charge curves of Li/Li+/LiyMxMn2−xO4 type cells and therein determined chemical diffusion coefficients of Li were shown. In the charge curves of Li/Li+/LiyMxMn2−xO4 cells, 2 visible plateaux separated with distinct potential jump (0.5–0.7V) were observed. The lower plateau was related to the Mn3+ → Mn4+ oxidation, while the next of higher voltage, of the Mm+ dopant oxidation. Substitution of Mn caused disappearance of the phase transition characteristic of a stoichiometric spinel. The schematic diagrams of relative Mn–M electronic levels alignment were proposed. It was shown that replacement of Mn by Cu and Fe improved both electrical conductivity and chemical diffusion coefficient of Li in the cathode materials.

The Effect of 3d Substitutions in the Manganese Sub-Lattice on the Electrical and Electrochemical Properties of Manganese Spinel. J.Molenda, J.Marzec, K.Świerczek, D.Pałubiak, W.Ojczyk, M.Ziemnicki: Solid State Ionics, 2004, 175[1-4], 297-304