Phase change material cooling method as a zero energy consumption cooling system has a good prospect in battery thermal management systems. Therefore, the thermal response of the lithium-ion battery in the presence of a phase change material was explored in this study. The lithium-ion battery was subjected to high discharge conditions (5 C-rate) at high ambient temperatures (35°C and 40°C). The results showed that the usage of phase change materials with a thickness of 1 mm can reduce battery temperature and deliver a better temperature difference in a lithium-ion battery. Results also revealed that for a 14.6 Ah lithium-ion battery under a 5 C discharge rate, a phase change material cooling system with a thickness of 1 mm can reduce the maximum temperature from 51.64°C at 35°C and 55.85°C at 40°C ambient temperatures (without phase change material) to 43.04°C and 43.81°C, respectively. It was concluded that the phase change material system with a thickness of 1 mm can manage the maximum battery temperature and temperature difference in the desirable range at an extreme discharge rate of 5 C. The results obtained from this study can be used as guidance in the design of battery thermal management systems including phase change materials.