Heat generation and thermal runaway mechanisms induced by overcharging of aged lithium-ion battery

Overcharging occurs owing to the malfunction of charge control and inappropriate battery management system. Overcharging mechanisms, aging mechanisms, and the influence of aging on overcharging are studied in this work. The results indicate that normal charging, lithium plating, electrolyte oxidation and decomposition, excessive electrolyte decomposition, and solid electrolyte interface decomposition and regeneration occur with charging. Much heat is produced in the reactions between lithium plating and the electrolyte, which is the main reason for thermal runaway during overcharging. The primary aging mechanisms of a battery cycled at 40 ℃ and 10 ℃ are solid electrolyte interface growth and lithium plating, respectively, where the former increases and the latter decreases the safety of the lithium-ion battery during overcharging. The trigger for thermal runaway during overcharging changes from a local, micro-level internal short circuit to solid electrolyte interface decomposition and regeneration when the state of health is less than 70 % cycled at 40 ℃. If the electrolyte is depleted and the temperature is less than that promoting cathode decomposition, thermal runaway does not occur during overcharging.