Isothermal calorimetry investigation of Li1+xMn2-yAlzO4 spinel

The heat generation of LiMn2O4, Lil(1.56)Mn(1.844)O(4), and Li1.06Mn1.89Al0.05O4 spinel cathode materials in a half-cell system was investigated by isothermal micro-calorimetry (IMC). The heat variations of the Li/LiMn2O4 cell during charging were attributed to the LiMn2O4 phase transition and order/disorder changes. This heat variation was largely suppressed when the stoichiometric spinel was doped with excess lithium or lithium and aluminum. The calculated entropy change (dE/dT) from the IMC confirmed that the order/disorder change of LiMn2O4, which occurs in the middle of the charge, was largely suppressed with lithium or lithium and aluminum doping. The dE/dT values obtained did not agree between the charge and the discharge at room temperature (25 degrees C), which was attributed to cell self-discharge. This discrepancy was not observed at low temperature (10 degrees C). Differential scanning calorimeter (DSC) results showed that the fully charged spinel with lithium doping has better thermal stability. (C) 2007 Published by Elsevier Ltd.