Parametrization of Lithium Ion Intercalation in Graphite for Battery Modelling

Abstract

Germany currently strives for CO2-free mobility for which electro mobility will be of major importance. For a good acceptance of the technology, electro mobility must be reliable and destinations at medium distances must be reachable. Both requirements presuppose precise range predictions and precise estimations of the battery status. The precision of both calculations relies on how adequate the underlying battery model represents the internal processes of a battery cell. This contribution examines the intercalation speed of lithium ions into the graphite anode in a physical-chemical battery model as main limiting parameter for fast charging due to the risk of plating. To minimize the risk of plating the intercalation process has to be fast enough to avoid large overpotentials. In the study described in this contribution, an optical-cell is used to analyze and understand the main characteristic parameters of the graphite material and further on these results are compared to the behavior of anode materials of commercial cells. Especially the reintercalation process of lithium ions of the anode overhang back in the active part of the anode is examined over time in commercial cells. The grain size as one of the main influencing parameters is already part of the model and is an important factor here. The measurement results of the setup are compared to the electrical data of the tested cell. Plating tests have already been performed and the plating has been confirmed with electrical measuring methods and laser microscope images. This submission looks into how the material and structural parameters of the graphite influence the intercalation speed of the lithium. Thus, an optimization route towards material design for fast charging can be deducted. These results help to gain a battery model that is based on battery material properties.