Battery thermal management system (BTMS) has significant impacts on the performance of electric vehicles (EVs). In this research, a computational fluid dynamics (CFD) coupled multi-objective optimization framework is proposed to improve the thermal performance of the battery pack having metal separators. CFD is utilized to study the thermal and fluid dynamics performance of the designed battery pack. Input parameters include inlet air temperature, thermal conductivity of coolant, thermal conductivity of metal separator, and diameter of heat dissipation hole. Five vital output parameters are maximum temperature, average temperature, temperature standard deviation (TSD), maximum pressure, and volume of the pack. The support vector machine (SVM) model is used to replace the real output parameters of the battery pack. Sensitivity analysis results indicate that the diameter of heat dissipation hole is the main factor affecting the volume of the structure and the pressure drop, while the inlet air temperature has significant influence on the battery pack thermal behavior. The cooling efficiency and the uniformity of temperature distribution are mainly determined by the inlet air temperature. The decrease of inlet air temperature could lead to a rise of temperature standard deviation. The nondominated sorting genetic algorithm-II (NSGA-II) is taken to acquire the optimum set of input parameters. The obtained optimal scheme of battery pack can improve the cooling efficiency as well as reducing the volume cost and the energy consumption of the cooling system while such design may result in a higher level of nonuniformity of the temperature and pressure distribution.

Temperature is a significant factor affecting performance and safety of energy storage systems such as battery packs. How to design a reliable battery thermal management system (BTMS) is still a hot issue at present. Most of the past researches have focused on methods of reducing temperature rise. This paper mainly studies how to reduce the temperature deviation of the battery pack while ensuring the heat dissipation conditions. This paper designs a mini-channel liquid cooling BTMS with side cover to improve heat transfer capacity and thermal uniformity in battery packs. By analyzing different side cover materials, cooling water temperature and water channel structure, the influence of different parameters on battery heat dissipation and uniformity is obtained. The main findings are: (1) The presence of the side cover can effectively reduce the maximum temperature and temperature deviation, the material with high thermal conductivity is more likely to dissipate heat. (2) The increase of cooling water inlet temperature can improve temperature uniformity. (3) When the cross-sectional area is fixed, as the channel depth increases, the temperature deviation gradually decreases.

Lithium-ion cells normally operate during 0% and 100% state of charge (SOC), therefore thermal runaway can occur at any SOC. In this paper, the 74 Ah lithium-ion pouch cells with the Li(Ni 0.8 Co 0.1 Mn 0.1 )O 2 cathode were thermally abused by lateral heating in a semi-open chamber. The differences of thermal runaway behavior were investigated under six SOCs. Characteristic parameters such as triggering time and triggering temperature for thermal runaway show a negative correlation with SOCs, while maximum surface temperature and maximum surface temperature rise rate show a strongly positive correlation. Besides, mass loss ratio increases exponentially with equivalent specific capacity statistically, which implies that the pouch cells with high specific energy density and high capacity may eject more violently. Furthermore, the impact on the surroundings caused by high-temperature ejections was studied, and maximum ambient temperature and maximum ambient pressure in the chamber reached a plateau at middle SOCs. Based on the thermal impact on the surroundings, a theoretical method is proposed to evaluate the deterioration of heat dissipation by venting, and simplified to quantitatively calculate the deterioration under above SOCs. The results can provide guidance for battery safety management strategies and structure design of the battery pack.

Thermal management system (TMS) plays an essential part in improving the safety and durability of the battery pack. Prior studies mainly focused on controlling the maximum temperature and temperature difference of the battery pack. Little attention has been paid to the influence of the TMS on thermal runaway (TR) prevention of battery packs. In this paper, a heat pipe-based thermal management system (HPTMS) is designed and investigated to illustrate both the capabilities of temperature controlling and TR propagation preventing. Good thermal performance could be achieved under discharge and charge cycles of both 2 C rate and 3 C rate while the equivalent heat dissipation coefficient of the HPTMS is calculated above 70 W/(m 2 ·K). In the TR propagation test triggered by overcharge, the surface temperature of the battery adjacent to the overcharged cell can be controlled below 215 °C, the onset temperature of TR obtained by the adiabatic TR test of a single cell. Therefore, TR propagation is prevented due to the high heat dissipation of the HPTMS. To conclude, the proposed HPTMS is an effective solution for the battery pack to maintain the operating temperature and improve the safety level under abuse conditions.