Degradation investigation of three Li-ion cell chemistries under different aging scenarios through differential voltage and post mortem analysis

This study aims to systematically examine aging mechanisms of lithium-ion cells. For this purpose, three different commercially available cylindrical cells featuring nickel-rich cathodes and graphite-based anodes are tested. Each cell type undergoes five different aging methods, encompassing calendar aging, cyclic aging and a realistic drive cycle profile. Differential voltage analysis is employed as a non-destructive technique to gain insights into degradation modes of the aged cells. The findings suggest that in the cells equipped with nickel-cobalt-aluminum cathodes and graphite/silicon anodes, the primary aging mechanism involves growth of the solid electrolyte interface. Conversely, cells incorporating nickel-cobalt-manganese cathodes with a higher silicon content in the anode, experience a notable loss in anode capacity. The obtained results from electrochemical tests are validated through post mortem analysis including scanning electron microscopy, mercury porosimetry, computed tomography, and coin cell measurements. Through material characterisation analysis, differential voltage analysis proves to be a reliable, non-invasive method for aging investigation.