Influence analysis of production defects of lithium-ion cells using single-cell and multi-cell characterization

To meet the challenge of significant expansion of vehicle electrification around the world, it is crucial for cell manufacturers to supply high quality lithium-ion cells for battery electric vehicle performance requirements at low scrap rates for both capital and competitive reasons. Hence, there is considerable interest in being able to inspect produced cells quickly and in high volumes, both by means of formation tests and in subsequent end-of-line tests. This article demonstrates and evaluates the detection of potential production defects during the formation and cell characterization process steps, presenting a novel method for simultaneous characterization of multiple lithium-ion cells in the context of cell production (multi-cell characterization method). 46 coin cells are assembled, with six different fault types induced, ranging from particle contamination to electrolyte and moisture deviations to varying formation temperatures. The results of the extensive single-cell characterization show that a differential voltage analysis performed at low currents allows a robust detection of all induced fault types, whereas conventional capacitance screening, direct current internal resistance techniques and electrochemical impedance spectroscopy measurements do not permit sufficiently accurate detection. In addition, the cell defects can also be detected using the presented multi-cell characterization with an economized number of required test channels.