Comparative analysis of cylindrical lithium-ion battery responses to continuous and intermittent compression: Insights into safety and failure mechanisms

Understanding lithium-ion battery failure under mechanical abuse is critical for safety. While continuous compression is studied, the effects of intermittent loading and its interaction with State of Charge (SOC) are less understood. This study experimentally investigates the mechano-electrochemo-thermal failure of 18650 NMC cells under continuous versus intermittent compression across various SOCs (20 %–80 %), monitoring mechanical, electrical, and thermal responses. Results revealed complex, non-linear failure mechanisms. High SOC consistently increased failure susceptibility (earlier failure, lower deformation tolerance). Intermittent compression proved significantly more hazardous than continuous loading, particularly at high SOC, accelerating internal damage and causing earlier, more severe thermal runaway, often initiated by identifiable soft short circuits (multi-stage voltage drops). Crucially, stiffness exhibited complex, mode-dependent behavior: non-monotonic under continuous compression (peaking at SOC 20 %) versus a generally monotonic increase under intermittent compression, highlighting loading pattern influence. The anode was the primary heat source during thermal runaway, and anomalous behavior was noted at SOC 60 %. These findings highlight the limitations of standard continuous crush tests and the need to incorporate intermittent loading in safety assessments. The complex, mode- and SOC-dependent mechanical responses provide critical data for robust battery pack design (considering stiffness variations and fatigue) and inform Battery Management System (BMS) failure precursor detection.