To meet the requirements of electronic vehicles (EVs) and hybrid electric vehicles (HEVs), the high en- ergy density LiNi 0.8 Co 0.15 Al0.05 O 2 (NCA) cathode and Si–C anode have attracted more attention. Here we report the thermal behaviors of NCA/Si–C pouch cell during the charge/discharge processes at different current densities. The total heat generations are derived from the surface temperature change during electrochemical Li + insertion/extraction in adiabatic surrounding. The reversible heat is determined by the entropic coefficients, which are related with open-circuit voltage at different tem peratures; while the irreversible heat is determined by the internal resistance, which can be obtained via V –I characteris- tic, electrochemical impedance spectroscopy and hybrid pulse power characterization (HPPC). During the electrochemical process, the reversible heat contributes less than 10％ to total heat generation; and the heat generated in charge process is less than that in discharge process. The results of thermal behav- iors analyses are conducive to understanding the safety management and paving the way for building a reliable thermal model of high energy density lithium ion battery.