The temperature control of Lithium-ion (Li-ion) cells plays a crucial role in enabling high current discharge performance. To address this, the present study explores the use of RT35 phase change material (PCM) and single-walled carbon nanotubes (SWCNT) as an additive approach to regulate the temperature of LiFePO4 Li-ion cells. By employing computational fluid dynamics (CFD), incorporating buoyancy force and a turbulent approach, an unsteady problem was simulated to investigate the effects of key parameters such as SWCNT concentration and PCM thickness. Notably, SWCNT addition exhibits a double effect, reducing liquid PCM volume and modifying temperature profiles. The average melting fraction at SOC = 100 % decreased from 100 % to 88 % with increasing PCM thickness from 9δ to 17δ, while it reduced the battery temperature by 3394 K to 331 K. Additionally, the impact of SWCNT volume fraction is most pronounced at 0.02, with similar effects observed at 0.04 and 0.06.