Development of Tests for Lithium-Ion Cell Characterization

The long-term degradation behavior of lithium-ion batteries is directly related to changes in the internal resistance of the cells. Reasons for the increase in resistance are i.e. growth of insulating surface layers, electrolyte decomposition, and loss of active material, blocked intercalation pathways and delamination effects. In this study commercial cells were aged with realistic load profiles. The internal resistance was investigated by the classic current pulse method (DIN EN 62660-1) as well as electrochemical impedance spectroscopy (EIS). First results of both measurements methods obtained in a CGR18650 cell are in good agreement. The advantage of EIS is that a lot of additional information about the main influencing factors to the overall resistance can be derived, whereas the pulse charging methods are advantageous due to their ease of application. Acknowledgments: We thank the Federal Ministry of Education and Research (BMBF) for funding this work (FKZ: 03X4636B).