Pulsed Preheating of High-Power and High-Energy Lithium-Ion Cells in Extreme Cold Temperature

Charging lithium-ion batteries at low temperatures presents significant hurdles, leading to accelerated aging degradation and safety concerns. Pulsed preheating is considered one of the most effective internal preheating techniques for elevating cell temperature to operational levels. This study investigates the pulsed preheating method applied to 21700 high-energy and high-power lithium-ion cells at −20°C across 30%, 50%, and 80% SOC levels. The experiments evaluate preheating performance under various C-rates and frequencies, while accounting for voltage constraints. Additionally, Electrochemical Impedance Spectroscopy (EIS) measurements are conducted to analyze the internal impedance of both cells at different temperatures for further experimental validation and theoretical analysis. The results demonstrate that at 30% SOC, the high-power cell preheats above 0°C in 250 seconds, showing a faster temperature rise than the high-energy cell, which requires 690 seconds; particularly at higher C-rates. At 50% SOC, the high-power cell successfully reaches above 0°C in 240 seconds using a 2C pulse current, whereas the high-energy cell fails to do so under the same conditions. In contrast, at 80% SOC, both cells are unable to preheat above 0°C as they operate near their maximum voltage limits. Overall, the high-power cell consistently outperforms the high-energy cell in pulse preheating due to its higher current capabilities and lower voltage drop, making it a more suitable candidate for rapid internal heating in subzero environments.