Impact of Testing Method on Safety Assessment of Aged Li-ion Cells: Part I – Li Plating as Main Aging Mechanism

Extending the lifetime of lithium-ion batteries is essential to maximize resource efficiency and minimize environmental impact. Therefore, understanding the aging mechanisms that batteries undergo in their first life is critical to ensure safe operation in second-life applications. This study focuses on a comprehensive safety assessment of commercial 18650-type lithium-ion batteries with graphite||NCA chemistry. The safety of aged cells with the aging mechanism of lithium plating was tested using thermal (ARC), electrical (overcurrent, overcharge, overdischarge), and mechanical (nail penetration) abuse tests. New cells without lithium plating serve as control samples for comparison of the different safety test types and for the cells with lithium plating. The presence and absence of lithium plating is confirmed by electrochemical tests and Post-Mortem analyses (SEM, GD-OES). The cells with lithium plating exhibit significantly lower onset of self-heating temperatures, a tendency to higher maximum thermal runaway temperatures and increased EUCAR hazard levels. The results highlight potential hazards associated with lithium plating in lithium-ion batteries and the necessity to detect and avoid lithium plating in first life in order to safely reuse them in second life applications. This is part one of two papers dealing with safety testing aspects of aged cells with different degradation mechanisms.