Li-ion battery is becoming a popular energy storage device in Hybrid Electric Vehicles (HEV) and Electric Vehicles (EV) due to its high energy density, high voltage and low self-discharge rate. The major concerns in designing Li-ion batteries are their life, performance and safety, which have close relations to their thermal behaviors. The temperature of Li-ion batteries rises during charge/discharge process. It goes faster especially with high charge/discharge rate during fast charging procedure. In this research, CFD models are developed based on ANSYS/FLUENT MSMD battery model coupled with electrochemical submodel-Newman, Tiedeman, Gu and Kim (NTGK) empirical model. Detailed simulation results are obtained in battery thermal and electrochemical behavior for different bi-cell electrode and current collector tab configurations. The temperature, potential, current density distribution at the battery length scale are determined, temperature gradient distribution is computed, and the maximum temperature at different discharge rate are also compared. The thermal investigation can provide valuable input for Li-ion battery design and analysis, especially for fast-charging batteries where heat distribution and cooling is critical for the battery design.