Lithium-ion batteries have a high energy content, which makes them a great option for mobile storage applications. However, there are some serious concerns regarding their performance in terms of uncontrolled overheating. In this study, an analytical thermal model is developed based on the integral transform technique to predict the temperature field in a cylindrical lithium-ion cell. The temperature rise and the thermal gradient, as the significant parameters for the safety and performance assessment of lithium-ion batteries, are investigated for the lithium-ion cell. Moreover, the thermal behavior of the lithium-ion cell is comprehensively studied for different thicknesses of the component layers. It is found that the optimum thickness of the positive active material, the negative active material, the positive current collector, and the negative current collector for the efficient thermal operation of the lithium-ion cell is 180, 34, 21, and 20 μm, respectively. Furthermore, the performance of the optimized jelly-roll is assessed for the different types of cylindrical lithium-ion cells. The results indicate that the 21700 cell has the best thermal performance for use in high charge/discharge applications.

In recent years, wall-bounded cross-flow heat exchangers have gained significant attention for battery cooling applications. Due to similarities in geometry, these systems are often evaluated based on the heat and flow knowledge of free cross-flow heat exchangers. To determine the reliability of this assumption, this study performs a numerical comparison of the thermo-fluid behavior of wall-bounded and free cross-flow heat exchangers. Both heat exchangers have similar dimensions, with transverse and longitudinal pitch ratios of 2.074 and 1.037, respectively, and are investigated at a Reynolds number of 40000 using the Unsteady Reynolds-Averaged Navier–Stokes (URANS) method. It is observed that the  transition model provides the most accurate predictions of the flow field when compared to available experimental data. The results suggest that for wall-bounded heat exchangers with an aspect ratio of 2 or larger, the flow behavior in the central flow region resembles that of a free heat exchanger, but with varying magnitudes due to the increase in velocity in the core region to counterbalance the reduction near the walls. The area-averaged mean Nusselt number from 2D and 3D models for free heat exchangers shows no significant difference compared to wall-bounded heat exchangers. However, there are considerable differences in the local Nusselt number distributions in the angular and spanwise directions. Overall, it is determined that certain conditions must be satisfied to ensure that applying the thermo-fluid characteristics of a free cross-flow heat exchanger to wall-bounded cross-flow heat exchangers in battery thermal management systems is accurate.

Recent studies have revealed that effective thermal management systems are necessary to maintain the performance, lifespan, and safety of lithium battery systems. A unique and novel modeling approach is presented in this work with the aim of estimating the thermal performance of air-based cooling systems for large-scale lithium battery packages. The overall model consists of sub-models, including an analytical model for battery cells and a numerical heat and flow model for the battery module, which are validated against experimental data and empirical correlations, respectively. The chosen approach implies that the sub-models can operate independently, allowing accurate transient simulations with reduced processing time. The model is employed to evaluate the effect of cell spacing on the thermal performance of an air-cooled battery system designed for a hybrid electric vehicle. The results demonstrate that the maximum temperature within the cells positively correlates with transverse and longitudinal pitch ratios; however, the maximum temperature difference in the module has a negative correlation with these pitch ratios. In contrast, temperature uniformity shows non-monotonic behavior, making it an applicable criterion to balance between temperature rise and thermal gradients. Moreover, considerable temperature non-uniformity is noted in the early rows, which becomes less significant as pitch ratios decrease.

A reliable battery thermal management system plays a crucial role in the safe, efficient, and long-term operation of a high-performance lithium battery system. This study evaluates the temperature rise, pressure drop, capacity loss, and cyclical cost of an air-cooled battery system consisting of 90 cylindrical battery cells placed ina staggered arrangement in the module. The effect of spacing between the adjacent cells and inflow velocity is investigated for the battery system operating at high charge/discharge rates of 3C and 5C. The results demonstrate that the hybrid model, which consists of the battery life model integrated with the simplified modeling approach for the thermal evaluation of battery packs, provides a cost-effective tool for multi-objective analysis and optimization of air-cooled battery packages.The results reveal that the air-based cooling system has the potential to fulfill the safety standards in all studied cases, and employing battery modules with larger cell spacing at a constant inflow velocity may reduce the maximum temperature, pressure drop, and cyclical cost by up to 2.14%, 93.36%, and 35.69%, respectively, while extending the lifespan of the battery system by up to 55.45%. However, it is found that the air-based cooling system approaches its limit of thermal performance at high inflow velocities. A novel index (MCR index) is proposed in this paper to characterize the limitationsassociated with adjusting cell spacing for air-based battery cooling systems. It is observed that for systems with an MCR index beyond 600, the effect of cell spacingon thermal performance becomes negligible. This can be used as a useful guideline for optimizing air-based battery thermal management systems or integratingthem with other cooling methods.

Considering the widespread incorporation of lithium batteries for different applications and the concerns regarding their safety and lifespan, the importance of developing efficient battery thermal management systems increases. In this work, splitter plates (SP), as a passive enhancement method, are attached to an air-cooled battery module consisting of 87 cylindrical 26650 LFP cells in a staggered arrangement to study their effect on the performance of the module at a 5 C charge/discharge rate. A hybrid modeling approach is employed to enable a multi-objective assessment of the system with minimal computational costs. The model includes a CFD model, evaluating the effect of SP on the thermo-hydraulic performance of compact systems as a present battery cooling system. In addition, an analytical thermal model and an empirical life model are linked to the CFD model to investigate the operation of the module, including maximum temperature, capacity fading, and cyclical costs. The Reynolds number is allowed to vary from 7600 to 28000, and the study is performed for SP with lengths ranging between 0.25-0.5625 of a cell's diameter. The results indicate that attachment and lengthening of SP enhance thermo-hydraulic performance, reduce maximum temperature rise, and extend the cycle life of the battery module. However, unlike the widely-spaced tube banks, using SP in the current case does not necessarily reduce the friction factor. Moreover, despite large values for the performance evaluation criterion (>3.4), the applied cyclical cost index demonstrates that modules with long SP are inefficient, where extended lifespans and lower working temperatures do not justify increased costs associated with airflow circulation.