The market share of electric vehicles has been growing at a faster pace in passenger vehicle segment to reduce automotive pollution. There are many variants of electric vehicle but of late battery powered electric vehicle gained attraction. The battery, the major source energy storage, is available in different types. Lithium-Ion batteries got wide acceptance due to imminent better properties relatively. However, its performance is sensitive to temperature variations due to high discharge rate and high ambient temperatures. To maintain batteries without thermal runaway, battery thermal management has become essential and forms an integral part of electric vehicle. Of late external and passive cooling with Phase Change Materials has gained attraction by researchers. The present work deals with the computational simulations, using ANSYS R21, carried out on a prismatic battery cell with varying cell thicknesses under high discharge rates with and without PCM. It is noted that PCM could bring down the temperature with increase in thickness of PCM satisfactorily. In addition, to PCM thickness, the battery cell thickness and cell’s overall volume, plays a vital role. Among the variations tried out, the lowest peak temperature is seen to be 316 K with 4 mm thick PCM under 5C discharge rate, for a thin cell or higher volume.