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 in situ quantify the wetting progress in lithium-ion cells with graphite-based anodes. A constant potential is applied to the cell immediately 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 accompanied by SEI film formation. By applying this procedure, the influence of different separators, cell formats and ambient temperatures on the wetting time is investigated. Furthermore, the wetting behavior of laser-structured electrodes is investigated as well as of electrodes with ceramic multilayer coating which can replace the standard separator. The results demonstrate that the interface between the separator and the electrodes plays a dominant role and mainly influences the wetting process of a lithium-ion cell. The findings point out the importance of using in situ methods to analyze the wetting process of lithium-ion cells.