The distributions of potential and reaction rates in a lithium ion battery during discharge process have great influences on the battery thermal characteristics. A two-dimensional electrochemical–thermal model has been developed for a cylindrical LiFePO4 battery by coupling the mass, charge, and energy conservations as well as the cell electrochemical kinetics. The model also includes battery current collecting tabs. The modeling results are validated for both the electrochemical performance and thermal behavior during galvanostatic discharge process. The modeling results agree well with the experimental data. The placement of the positive and the negative current collecting tabs on the cylindrical battery was found to have a significant effect on the distributions of its potential and local reaction rates, which therefore affect heat generation rates, and thus the distribution of the temperature within the battery.