Numerical Investigation of Passive Thermal Management of Batteries in Electric Vehicle Using Nano Enhanced Phase Change Materials

ABSTRACT
Effective thermal management of lithium‐ion batteries is essential to ensure the safety, reliability, and longevity of electric vehicles, since excessive heat generation at high discharge rates accelerates degradation and may lead to thermal runaway. Passive battery thermal management systems employing phase change materials (PCMs) provide an energy‐efficient means of regulating temperature; however, their inherently low thermal conductivity restricts melt‐fraction utilization and results in non‐uniform heat dissipation. To overcome this limitation, enhancing PCMs with highly conductive nanoparticles has emerged as a promising strategy for improving thermal transport and phase‐change efficiency. In this study, the thermal response of a cylindrical 18650 is numerically examined under three configurations: a bare cell, PCM encapsulation (RT35), and nano‐enhanced PCM encapsulation (RT35 + 5 wt.% Al₂O₃), at discharge rates of 1C, 2C, and 3C. A coupled Newman–Tiedemann–Gu‐Kim (NTGK) electrochemical–thermal model and enthalpy–porosity method was employed to capture heat generation and latent heat absorption. Results show that PCM encapsulation reduced peak temperatures by 2.1, 6.4, and 10.7 K compared to the bare cell at 1C, 2C, and 3C, respectively, though incomplete melting restricted effectiveness. Nano‐PCM further improved heat spreading and uniformity, lowering maximum temperatures by 2.33, 6.42, and 11.49 K compared to the bare cell. In overall the nano‐enhanced PCM (RT35 + 5 wt.% Al₂O₃) achieved the best thermal performance, reducing the peak temperature of the 18650 cell by up to 11.49 K at 3C compared to the bare cell. These findings validate nanoparticle‐enhanced PCMs as a scalable passive cooling strategy, providing deeper melt utilization and suppressed hot spots under high‐rate cycling. The coupled NTGK–enthalpy framework offers a predictive tool for designing next‐generation battery thermal management system with enhanced safety margins and operational reliability.