Electric and hybrid electric vehicles are promising alternatives to tackle environmental impact and greenhouse gas emissions associated with internal combustion engine vehicles. Electric vehicles have fueled the need for an efficient energy storage system to provide high power output, maximum energy density, and rapid charging. Lithium-ion batteries are a viable alternative as their high power density and energy capacity make them stand out from their long lifespan and quick charging capabilities. However, thermal energy generated during charging and discharging can cause safety concerns. In this regard, an experimental study was conducted to assess cooling performance using four distinct phase-change-materials (PCM): PARA-Block, RT-54 HC, RT-44 HC and RT-35 HC were tested in a cyclic test, which showed a reduction in the battery's maximum temperature to 59.6 °C, 57.6 °C, 50.9 °C, 51.9 °C respectively, compared to 76.4 °C with natural convection cooling. For further modification to achieve the cell's optimum operating temperature and shape stabilized material, various weight percentages of expanded graphite (EG) (3 %, 6 %, 12 %, 15 %) were added to obtain composite stable phase change material (CPCM). The results showed that the battery's highest temperature decreased by almost 55 % by adding 12 % EG to PCM RT 35 HC compared to natural cooling. In addition, the best conditions were applied for a four-battery pack.