Experimental study on the boundary of external short-circuit protection of Lithium-ion batteries

This study examines external short-circuit (ESC) mechanisms in lithium cobalt oxide (LiCoO₂) pouch cells, emphasizing their role in lithium-ion battery (LIB) safety incidents due to rapid energy discharge and transient currents. By testing under varied external resistances and durations, electrical-thermal-mechanical responses, degradation patterns, and safety thresholds were analyzed. Results demonstrate that reduced external resistance intensifies temperature rise (up to 74.8°C) and capacity loss, with ESC evolution categorized into five stages: initial surge, polarization, stabilization, destruction, and termination, each exhibiting unique thermal-electrical interactions. Post-ESC states are classified as no degradation, performance loss, unrecoverable voltage, leakage, or thermal runaway, with critical performance, failure, and safety boundaries linked to normalized resistance-duration thresholds. Voltage/current rate abrupt changes during short-circuiting serve as leakage indicators. Electrochemical analyses reveal increased ohmic and charge transfer impedances at lower resistances, driven by SEI growth and active material loss. The findings establish correlations between resistance, degradation pathways (anode/cathode material loss, lithium depletion), and safety limits, offering practical guidelines for ESC risk assessment and battery management system optimization.