Thermal performance of nano-enhanced phase change material and air-based lithium-ion battery thermal management system: An experimental investigation

The current investigation focuses on the design and development of an innovative thermal management system for lithium-ion batteries (LIBs). The primary objective is to assess the cooling efficiency of this system for cy-lindrical 18650 LIB cells through experimental observations conducted at various discharging rates i.e. 0.58C, 1.08C, and 1.38C. There are two distinct cooling approaches, namely passive and hybrid that are employed to diminish the maximum average temperature of the battery module and ensure adequate temperature uniformity. In the current investigation, three discrete grades of paraffin wax are employed as phase change materials (PCMs) with varying melting points: PCM1 with a melting point >60 degrees C, PCM2 with a melting point around 53 degrees C, and PCM3 with a melting point below 40 degrees C. PCM2 exhibits the highest decrease in the rise of battery module temperature at considered discharging rates. Additionally, the temperature distribution within the battery module is more uniform in comparison to the other PCMs. The study includes the preparation and utilization of nano-enhanced PCM (n-PCM2) using Al2O3 nanoparticles with different weight fractions (phi(wt)) i.e. 2 % and 4 %. The highest decrease in the maximum average temperature of the battery module for the case of n- PCM2 at phi wt of 2 % and 4 % is 23 % and 27 % compared to the no-cooling case. In addition, forced air cooling at different flow rates is used in conjunction with the passive cooling provided by the n-PCM2. The n-PCM2 with phi(wt) 4 % at 4 m/s exhaust air velocity demonstrates the highest reduction in the average temperature of the battery module by approximately 40 %, with temperature drops of 12.1 to 19.7 degrees C under different discharging rates. Furthermore, good temperature uniformity in the battery module is observed in the case of n-PCM2 at phi wt of 4 % and the n-PCM2 at phi wt of 4 % with air cooling demonstrates superior temperature uniformity, ensuring that the Delta T-max remains <3.5 degrees C at all discharging rates.