Non-Destructive Detection of Local Aging in Lithium-Ion Pouch Cells by Multi-Directional Laser Scanning

Understanding the mechanical activity of lithium-ion cells during cycling and its connection with aging phenomena is essential
to improve cell design and operation strategies. Previous studies of lithium-ion pouch cells [B. Rieger et al., Journal of Energy
Storage, 8, 1 (2016)] have shown non-uniform swelling with local displacement overshoots during charging. In this experimental
work, a novel three-dimensional laser scanning method is used to investigate local reversible and irreversible thickness changes of
six commercial LiCoO2/graphite cells during a cyclic aging experiment. Three cycle scenarios were included and two cells each
were exposed to a specific temperature and charging rate. The cells showing local displacement overshoots also exhibit non-uniform
distributions of irreversible thickness change. Post-mortem analysis showed largely inhomogenously degraded surfaces of the single
anode layers. It is shown that the cells’ irreversible thickness change correlates with capacity fade and internal resistance increase
monitored via electrochemical impedance spectroscopy.