As a shift toward electrical mobility has been noticed in recent years, so to cope with the increasing demand for EVs there is a need to develop an efficient thermal management system for the popular Lithium-ion batteries. This paper deals with designing an optimum thermal management system for a 6s4p Lithium-ion battery cell module. The study illustrates the time-dependent variation of temperature within the module. Initial simulation is carried out at 3C rate, without the application of PCM. It was observed that the maximum temperature during the charging case reached around 42 °C after 1000 s which is clearly outside the safe temperature limit of the module. Then for the same configuration, simulation is carried out by using Paraffin as PCM within the gap between cells and at the top and bottom where series and parallel connectors are installed. The graph recorded a maximum temperature of 34 °C which is approximately equal to the melting temperature of Paraffin. The temperature contours for both cases suggested how PCM is effective in reducing hotspot regions within the battery module. The study is further extended to charging rates of 1.5 and 2C. It is observed that with an increase in the C rate the temperature within the pack increase. Without PCM, the peak temperature difference between 1.5 and 3C case is 11 °C whereas with PCM the difference is reduced to 3.5 °C. Hence, PCM helps in the deployment of the battery in applications demanding a high current rate.