The ability to monitor the status of a battery during charge and discharge is important for predicting its performance and life. This is typically done by measuring the voltage and resistance across the terminals, or by external characterization methods such as X-ray diffraction and Raman spectroscopy. Thermodynamics measurements based on entropy and enthalpy provide another mean to “look inside” a battery, giving us more information to determine the state of health of the battery. In particular, entropy undergoes drastic changes at boundaries of phase transitions taking place in each electrode material at defined states of charge (lithium stoichiometry). Recent work on thermodynamics study on lithium ion battery materials is summarized in this paper.