An Analysis of a Lithium-ion Battery System with Indirect Air Cooling and Warm-Up

Ideal operation temperatures for Li-ion batteries fall in a narrow range from 20 degrees C to 40 degrees C. If the cell operation temperatures are too high, active materials in the cells may become thermally unstable. If the temperatures are too low, the resistance to lithium-ion transport in the cells may become very high, limiting the electrochemical reactions. Good battery thermal management is crucial to both the battery performance and life. Characteristics of various battery thermal management systems are reviewed. Analyses show that the advantages of direct and indirect air cooling systems are their simplicity and capability of cooling the cells in a battery pack at ambient temperatures up to 40 degrees C. However, the disadvantages are their poor control of the cell-to-cell differential temperatures in the pack and their capability to dissipate high cell generations. In contrast, the advantages of direct and indirect liquid cooling systems are their good control of the maximum cell temperature and maximum differential cell temperatures in the pack and their capability of dissipating high cell heat generations with good thermal uniformity. However, high ambient temperatures may limit the applications of liquid cooling systems because the performance of the radiator for cooling the liquid coolant deteriorates significantly with increasing ambient temperature. Thermal behavior is analyzed in detail of a module stacked with 12 high-power Li-ion pouch cells with indirect air cooling and warm-up. Simulation results show that with air cooling channels structured similar to that of compact heat exchangers, excellent heat-transfer performance of the air flow channels can be achieved for both cooling and warm-up. This suggests that the air-cooling-channel structure proposed in this study is appropriate for applications in active battery thermal management systems.