Effects of Low-Temperature Pre-Cycling on High-Temperature Degradation of Lithium-Ion Cells

Abstract

Lithium-ion (Li-ion) batteries suffer accelerated degradation when the operating temperature is beyond the optimal range1, 2, about 20 °C to 35 °C. At lower temperatures and higher temperatures, lithium plating and solid-electrolyte interface (SEI) growth are dominating degradation mechanisms, respectively1. A previous work by our group3 showed interestingly that pre-cycling Li-ion cells at 5 °C reduced degradation during cycling at higher temperatures of 45 °C and 60 °C. The observation suggested that low-temperature pre-cycling has significant effects on high-temperature degradation of Li-ion cells. The previous work was based on small cells that consisted of a single pair of electrodes. To confirm if the phenomenon also exists in large cells that consist of multiple pairs of electrodes, commercially available 3-Ah pouch cells are tested. It is found that pre-cycling of these large cells at 5 °C also significantly reduces their degradation at 45 °C. However, this effect is observed only when the cells are compressed. Without compression, cells pre-cycled at 5 °C degrade much faster than baseline cells cycled only at 45 °C. Further analysis of the results, such as cell internal resistance analysis and electrochemical impedance spectroscopy, is performed to better understand the effects of low-temperature pre-cycling on high-temperature degradation behaviors of Li-ion cells.