Increasing the cycle life of lithium-ion batteries is one major objective in state-of-the-art battery research. However, the underlying highly complex aging mechanisms are still not sufficiently understood. In the present contribution, we investigate the 3D microstructure of cyclically aged electrodes and correlate it with their electrochemical properties. More precisely, synchrotron tomography is used to capture the morphology of lithium-ion batteries with a state of health of 100%, 90%, 80%, 60% and 40%, where two different C-rates (0.5C and 1C) have been used for each cycled state. The three phases, i.e., active material, pores and the phase consisting of binder and conductive additives, have been reconstructed from the 3D grayscale images by a k-means cluster approach, similar to [1]. Moreover, individual active particles are segmented by combining morphological reconstruction by means of the watershed algorithm. The processed image data allows to quantitatively characterize the 3D microstructure by phase-based as well as particle-based characteristics, where a particular focus is put on the heterogeneity of the electrode, which is described by locally computed geometric descriptors. In addition to structural aspects, electrochemical data are used to further characterize the cyclically aged cells. Finally, we correlate structural and electrochemical properties to obtain a deeper understanding for the underlying aging mechanisms.

[1] Benedikt Prifling, Alexander Ridder, Andre Hilger, Markus Osenberg, Ingo Manke, Kai Peter Birke, and Volker Schmidt. Analysis of structural and functional aging of electrodes in lithium-ion batteries during rapid charge and discharge rates using synchrotron tomography. Journal of Power Sources 443, 227259, 2019.