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 the degradation mechanism of the aged cells. The analysis of aging mechanisms using DVA revealed a consistent primary aging mechanism at lower SoH across all applied aging conditions for the three tested cell types. 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. Additionally, it is indicated that aging modes may be influenced by the stage of aging in particular cell types and must be considered in data analysis.
The obtained results from electrochemical tests are validated through post mortem analysis including scanning electron microscope analysis, mercury porosimetry, and computed tomography. Through material characterisation analysis, differential voltage analysis proves to be a reliable, non-invasive method for aging investigation.