In order to disclose the decomposition kinetics of charged LiMn 2 O 4 used in lithium-ion batteries, thermogravimetric analyzer (TGA) and C80 micro-calorimeter were employed in this study. Three stages of weight loss were detected by TG and two main exothermic processes were detected by C80 micro-calorimeter for the charged LiMn 2 O 4 . The chemical reaction kinetics is supposed to fit by an Arrhenius law, and then the activation energy is calculated as E a =90.4 and 140.1kJmol −1 based on TG and C80 data, respectively. And the C80 method shows more advantages in studying the thermodynamic and kinetic parameters for both the electrodes alone and its co-existing system with electrolyte.