Cyclic voltammetry (CV) of LiNi0.8Co0.2O2/Li half-cell and mesocarbon microbead (MCMB)/Li half-cell are studied at very low scan rates. The thermal behaviors of these two half-cells and LiNi0.8Co0.2O2/MCMB full-cell cycled at different current levels are studied with electrochemical-microcalorimeter technique in terms of reversible and irreversible heat generation. The calculated results show excellent agreement with the experimental data at low and moderate current levels (≤C/4). The quantitative heat contributions of the cathode and anode to the overall cell heat generation are also determined.