| Abstract | Lithium-ion (Li-ion) batteries have significantly deteriorated energy and power performance when used at extremely low temperature, which creates difficulties when deployed in applications within cold climate. Battery preheating is critical in this aspect to improve the performance of Li-ion cells. In this work, polyimide film heaters are used to selectively preheat commercial pouch type battery cells with large terminal tabs that have been exposed to sub-zero temperatures. Two heating configurations, surface heating and tab heating, are compared in terms of their heating power, heating time, hot spot development, and temperature uniformity. Surface heating can preheat the cell from −30 °C to 0 °C in 5 min, while tab heating overheats the tabs when a high heating power is applied. Thermal modelling is then used to investigate heat transfer resistances during the tab heating configuration by adjusting the dimension of current collector and electrode tab, as well as the thermal contact resistance at the interface between the tab and current collector. Larger tabs are found to be helpful in reducing the tab temperature. However, state-of-the-art OEM cells are not equipped with such tabs that support tab heating. Finally, the durability test is performed on both the original and preheated cells, during which 10% and 22% capacity losses are found on the cells after 1000 charge/discharge cycles and 500 preheating cycles, respectively. Morphological and electrochemical analyses are conducted to investigate the fading mechanism, and it reveals that active materials and lithium ions losses lead to the degradation of performance and durability. |
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