Chronoamperometry as an electrochemical in situ approach to investigate the electrolyte wetting process of lithium-ion cells

Understanding and optimizing the electrolyte wetting of lithium-ion cells provides a high potential to reduce the manufacturing costs of lithium-ion cells. However, established methods to investigate the wetting of porous materials are not easily transferable to lithium-ion cells, since they neglect major paths in the wetting process. In this study, a novel method is proposed to quantify the wetting progress in situ in lithium-ion cells with graphite-based anodes. A constant potential is applied to the cell after the electrolyte wetting process has been initiated and the current response is carefully analyzed as it reflects the progress of the electrolyte wetting process. The influence of the separator, ambient temperature and the cell dimension is investigated. Furthermore, the wetting of structured and surface-coated electrodes is investigated. The results demonstrate that the interface between the separator and the electrodes plays a dominant role in the wetting process of a lithium-ion cell. Furthermore the measurements provide valuable insight into optimization potentials of the manufacturing process, especially of large format cells, and point out the importance of using in situ methods to analyze the wetting process of lithium-ion cells.