Thermal management is essential for the lithium-ion batteries of electric vehicles to maintain a suitable temperature range and reduce local temperature differences. In this study, a multichannel wavy tube is proposed for a liquid cooling cylindrical lithium-ion battery module. Three-dimensional (3D) transient simulations were conducted on the proposed battery module, and numerical optimizations were performed by varying the wavy contact angle and mass flow rate of the multichannel wavy tube. An increase in wavy contact angle and mass flow rate positively affects the heat dissipation efficiency and temperature field homogeneity of the battery module. However, the positive effects decline as the same amount of wavy contact angle or mass flow rate is increased because the wavy tube reaches its limit in cooling the battery module. Experiments under corresponding working conditions were performed to validate the heat transfer performance of the battery module. Simulation results will provide specific reference values for the thermal management of cylindrical lithium-ion battery modules.

An electrochemical-thermal coupling model combined with an electrically connected cylindrical cell model was built to produce a structural design that prevents thermal runaway propagation of cells on the battery module. Additionally, the characteristics of different modes of heat transfer of each cell during thermal runaway propagation of the battery module in an open environment were studied by changing the spacing of adjacent cells, the solder joint area, and the cross-sectional area of the electrode tab. Heat conduction is usually the main heat transfer mode for cells directly connected to the thermal runaway cell, while radiation heat transfer is the main heat exchange mode for cells that are not directly connected to thermal runaway cell. Increasing spacing can prevent thermal runaway propagation by the three heat transfer modes. Similarly, a smaller total solder joint area and cross-sectional area of the electrode tab can inhibit thermal runaway propagation through heat conduction transfer modes if conditions permit.

An effective battery thermal management system (BTMS) is essential for controlling both the maximum temperature and the temperature uniformity of a battery module. In this study, a novel and lightweight BTMS for prismatic batteries based on a heat pipe is proposed. A numerical model is created to study the influence of heat transfer designs and other factors on the thermal performance of the BTMS, and the simulation results are checked experimentally. The results show that when the condensation section of the heat pipe is cooled by liquid, the maximum temperature of the battery (T_max) is reduced by 18.1% compared with air cooling. Decreasing the coolant temperature can reduce T_max, but can also lead to an undesirable temperature nonuniformity. The T_max and the maximum temperature difference (ΔT_max) in a battery module both increase rapidly as the discharge rate rises. The T_max and ΔT_max are lower than 40 °C and 5 °C respectively when the discharge rate of the battery is lower than 2C. Under preheating conditions in cold weather, increasing the temperature of the heating medium can improve the temperature of the batteries, but at the same time it can make the battery module's temperature more nonuniform, and also add to cost. The temperature of the heating medium should therefore be selected with care. It could be concluded that the above results can provide perspectives in designing and optimizing battery thermal management system.