Lithium-ion battery (LIB), as a renewable energy storage device has received considerable attention in recent years for its zero-emission, long life, and high energy density. However, the performance, lifespan, and safety of the LIB systems are greatly affected by their operation and storage temperatures. To ensure the batteries to work in the optimum temperature range, various battery thermal management systems (TMS) have been investigated. This research focuses on the numerical study of the thermal performance of a hybrid battery cooling system which consists of an integrated forced cooling (e.g., liquid flow in a cold plate) and phase change materials (PCM) composite — a graphite foam impregnated by paraffin wax. In the numerical model, the non-equilibrium thermodynamics model and Darcy’s law are utilized to simulate the thermal and momentum transports in the PCM composite. The heat generation rates of the battery cells are mainly determined by the depth-of-discharge (DOD) dependent internal resistance. In addition, the numerical model takes into consideration the anisotropic axial and radius thermal conductivities of the LIB battery. The results show that PCM composite plays a critical role in achieving the temperature control and maintaining the temperature difference of the LIB battery module. The melting rate of paraffin wax in the graphite foam is directly related to the coolant flowrate, coolant inlet temperature, porosity of the graphite foam, and the internal resistance of the LIB battery.