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The charging/discharging characteristics and life cycle of a lithium-ion battery are significantly dependent on the battery thermal performance. In this study, the three-dimensional numerical model was developed to explore the effects of thermal conductivities of the battery, holding plate, and diameter of venting holes on the thermal behaviors of the stagger-arranged battery pack cooled by longitudinal airflow. The numerical model was validated by our previous experimental results. Numerical results illustrated that the thermal conductivities of the battery and holding plate have nearly no effect on the thermal behaviors of the 18650 lithium-ion battery pack; therefore, the traditional epoxy (khp=0.2 W·m−1·K−1) is an effective material for the holding plate with the advantages of low cost, excellent insulation, and thermal conductivity properties. The heat-transfer coefficient between the air coolant and battery or holding plates does not gradually decrease along the horizontal airflow direction due to the periodic thinning and damaging of the flow boundary layer caused by the venting holes, which indicates that the venting holes can improve the overall heat-transfer performance of the battery pack. At last, comprehensively considering the effects of the diameter of the venting holes on thermal characteristics, cooling efficiency, and structural strength, the appropriate diameter of the venting holes should be 4 mm for the 18650 lithium-ion battery with holding plates. [ABSTRACT FROM AUTHOR]

Summary: The reliable thermal conductivity of lithium‐ion battery is significant for the accurate prediction of battery thermal characteristics during the charging/discharging process. Both isotropic and anisotropic thermal conductivities are commonly employed while exploring battery thermal characteristics. However, the study on the difference between the use of two thermal conductivities is relatively scarce. In this study, the isotropic and anisotropic thermal conductivities of the four commercially available lithium‐ion batteries, ie, LiCoO2, LiMn2O4, LiFePO4, and Li (NiCoMn)O2, were reviewed and evaluated numerically through the heat conduction characteristics inside the battery. The results showed that there are significant differences in the temperature distribution in the battery caused by the isotropic and anisotropic thermal conductivities, which could affect the layout and cooling effectiveness of battery thermal management system. Furthermore, the effective thermal conductivities of porous electrodes and separator were determined to establish thermal conductivity bounds of lithium‐ion batteries combined with the thicknesses of battery components. The thermal conductivity bounds could be applied to evaluate the rationality of the thermal conductivity data used in battery thermal models. [ABSTRACT FROM AUTHOR]

• Heat generation behavior of battery with Li(Ni x Co y Al z)O 2 cathode is obtained by ARC. • Maximum temperature and temperature difference in battery pack can be maintained properly by natural cooling. • Forced air cooling strategy with longitudinal airflow significantly reduces temperature rise in battery pack. • Air cooling with flow velocity of 0.8 m⋅s−1 is recommended for achieving appropriate DOD of 84.2%. The thermal characteristics of lithium-ion battery affect significantly charging/discharging performance, cycle life and safety of electric vehicles (EVs) battery packs. In this study, a stagger-arranged battery pack consisting of three battery modules was developed to explore its transient thermal characteristics in charging/discharging process under the two cooling strategies, i.e., natural cooling and forced air cooling. The investigation of heat generation behavior of the battery with Li(Ni x Co y Al z)O 2 cathode showed that the heat generation rate of the battery remains almost unchanged along the main discharging process, while a rapid increase in heat production is detected at the end of discharging. It was found that the maximum temperature and temperature difference in the battery pack subject to a moderate charging/discharging rate, e.g., 0.5 C, can be maintained within the desirable ranges by natural cooling. The forced air cooling strategy employing longitudinal airflow remarkably improves the battery's transient thermal characteristics with achieving the depth of discharge (DOD) up to 84.2%, which is capable to prolong the battery pack's cycle life to a large extent. Lastly, the appropriate air supply velocity of 0.8 m⋅s−1 is recommended for the proposed battery pack subject to a higher discharging rate, e.g., 1 C, from the viewpoint of cooling effectiveness. [ABSTRACT FROM AUTHOR]