Avoiding thermal runaway during spent lithium-ion battery recycling: A comprehensive assessment and a new approach for battery discharge

Discharge is a critical step to decrease the risk of explosion and fire in the recovery of spent lithium-ion battery (LIB). This study is the first to provide a comprehensive and detailed assessment of the discharge process of spent LIB. The thermal runaway was analyzed through the voltage, state of charge (SOC), battery status and dismantling of spent LIBs under different discharge degrees. The results show that the spent LIB could be safely disassembled when the voltage was lower than 1.5 V (SOC<5%). Under the guidance of comprehensive assessment, this paper developed a new method for fast and efficient discharge of spent LIBs. By using graphite electrode to replace battery tabs for discharge, the corrosion of battery could be avoided, and the discharge speed was faster and more thorough in reductant-ultrasonic system. Compared with traditional electrolyte solution (NaCl), the voltage of battery was easier to drop to 1.5 V, and the overall discharge time had been shortened by 3/4. Finally, abuse experiments show that the new discharge method and assessment results were reliable. Therefore, this study provides an important reference for the discharge of spent LIB and is more conducive to the safe recycling of spent LIB.