Experimental analysis of thermal management in li-ion batteries with nano-reinforced paraffin-based phase change material

The safe, efficient, and long-term operation of lithium-ion (Li-iyon) batteries used in electric vehicles (EV) depends on maintaining the battery temperature within appropriate limits. In this context, battery thermal management has become one of the critical components of electric vehicle technologies. In this thesis, paraffin-based phase change materials (FDM) were developed and experimentally investigated in order to enhance the passive cooling performance of Li-iyon batteries. Within the scope of the study, composite PCMs were prepared by incorporating different types of nano-additives, namely aluminum nitride (AlN), magnesium oxide (MgO), and boron nitride (BN), into the paraffin matrix at various weight ratios (2%, 5%, and 7%). The developed FDMs were tested on two different battery pack geometries (flat and square) consisting of 18650-type Li-iyon cells connected in a 2-series 2-parallel (2S2P) configuration. The experiments were conducted at ambient temperatures of 20 °C and 40 °C. During the experimental analyses, the temperature variations of the battery cells were monitored, and the thermal performance was evaluated based on key thermal indicators such as the inter-cell temperature difference (ΔT), maximum temperature (Tmax), temperature rise magnitude, and temperature rise rate (SAH). The results demonstrated that composite PCMs containing nano-additives significantly reduced both the battery temperature rise and the temperature rise rate compared to the additive-free paraffin structure. In particular, composite PCMs with higher loadings of AlN and MgO exhibited better thermal performance under different test conditions. The findings obtained in this thesis indicate that paraffin-based PCMs reinforced with nano-additives provide an effective, practical, and low-cost passive battery thermal management solution for Li-iyon battery systems.