Abstract The heat generation of LiMn 2O 4, Li 1.156Mn 1.844O 4, and Li 1.06Mn 1.89Al 0.05O 4 spinel cathode materials in a half-cell system was investigated by isothermal micro-calorimetry (IMC). The heat variations of the Li/LiMn 2O 4 cell during charging were attributed to the LiMn 2O 4 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 (d E/d T) from the IMC confirmed that the order/disorder change of LiMn 2O 4, which occurs in the middle of the charge, was largely suppressed with lithium or lithium and aluminum doping. The d E/d T values obtained did not agree between the charge and the discharge at room temperature (25 °C), which was attributed to cell self-discharge. This discrepancy was not observed at low temperature (10 °C). Differential scanning calorimeter (DSC) results showed that the fully charged spinel with lithium doping has better thermal stability.