Experimental investigation of passive thermal management in Li-ion battery pack using eutectic phase change materials for electric vehicles

Lithium-ion (Li-ion) batteries are the favored energy source for electric vehicles because of their high energy density, low self-discharge, long lifespan, lack of memory effect, superior performance, high specific energy, and excellent efficiency. However, working under extreme environments and high C-rates can produce significant heat within the battery pack. This extra heat can diminish performance and potentially trigger thermal runaway. To guarantee a Li-ion battery pack operates optimally, an efficient cooling system is required. This study experimentally investigates a passive phase change materials (PCMs) cooling method using eutectic organic PCMs during charging and discharging of battery pack at high C-rates. The eutectic PCMs include lauric acid/myristic acid (LA/MA) and lauric acid/palmitic acid (LA/PA). They have melting temperatures of 35.73 °C and 36.25 °C, thermal conductivities of 0.357 W/mK and 0.306 W/mK, and latent heats of 162.33 J/g and, 182.73 J/g respectively. The results reveal that, in the absence of PCM cooling, the maximum temperatures of the Li-ion battery pack were 52.8 °C, 61.2 °C, 75.2 °C, and 87.3 °C at discharge rates of 1.5C, 2C, 2.5C, and 3C, respectively. In comparison to without PM cooling methods, the LA/PA eutectic PCM achieves a maximum efficiency of 31.5 %, while the LA/MA eutectic PCM achieves a maximum efficiency of 34.0 %. These results could substantially reduce the peak temperature of Li-ion cells and offer valuable insights for designing passive cooling systems in Electric vehicles. • Binary eutectic PCMs of LA/SA and LA/MA were prepared and thermally analyzed. • LA/SA and LA/MA melted at 36.25 °C and 35.73 °C with good heat storage capacity. • Thermal conductivities of LA/SA and LA/MA were 0.306 W/m·K and 0.357 W/m·K. • Eutectic PCMs enhanced battery cooling by 31.5 % and 34.0 % at high C-rates.