Electrochemical-calorimetric measurements were employed in this study to disclose the thermo-electrochemical behaviors of LiMn2O4 lithium-ion cells during charge–discharge process at various charge–discharge rates. The results showed that the specific capacity and the amount of heat were strongly affected by the charge–discharge rate. The specific capacity decreased and the amount of heat increased with increased rate. At low rate (0.1C and 0.2C), the cell exhibited smaller polarization and better reversibility, in which both reversible and irreversible heat contributed to the overall heat production, whereas the irreversible heat dominated the overall heat production when the cell cycled at high rate (0.5C, 1.0C, and 2.0C). A series of thermodynamic parameters of lithium-ion cells during the charge–discharge process, such as enthalpy change, entropy change and Gibbs free energy change, were achieved through the study of thermo-electrochemistry. These experimental results provided basic data for the battery thermal management and a new technique for a comprehensive evaluation of the thermal and electric performance of battery materials.