Numerical Investigation: Thermal Management of Lithium-Ion Batteries in Electric Vehicles Operating at High Discharge Rates

The present study develops and analyses a novel thermal management system that utilizes a serpentine cooling plate with fluid flow channels to regulate the temperature of cylindrical lithium-ion batteries in an electric vehicle battery module. The research investigates the impact of many variables affecting the cooling efficiency during discharge processes, including C-rate, number of cooling channels in the cooling plate, inlet fluid velocity and aluminium nanoparticle concentration in the fluid. The study includes 49 lithium-ion batteries with a capacity of 4.9 Ah each using NMC chemistry and a form factor of 21700 connected in series and parallel. A coolant made of water-glycol combination in 70:30 ratio is considered to disperse the thermal energy generated in the batteries. With the increase in the number of cooling channels, the maximum temperature of the batteries is reduced significantly. Increasing the cooling fluid's velocity reduces the batteries' maximum temperature remarkably. The batteries located at the centre of the battery module exhibit greater temperatures than batteries at the other locations, creating a temperature non-uniformity in the battery module. The temperature non-uniformity and the maximum temperature of the batteries were further reduced by adding the aluminium nanoparticles to the water-glycol mixture. The findings demonstrate that for a 1C battery discharge rate, a 4-channel cooling plate with 1% nanoparticle volume fraction and 0.025 m/s fluid velocity maintains the maximum temperature of the batteries below 304.54 K and the temperature difference below 4.6 K. For a 2C battery discharge rate, the maximum temperature and the temperature difference are attained below 306 K and 5 K by using a 6-cooling channel cooling plate with 1% nanoparticles and 0.075 m/s fluid velocity.