Comparative study of chemical discharge strategy to pretreat spent lithium-ion batteries for safe, efficient, and environmentally friendly recycling

The residual electricity contained in spent lithium-ion batteries probably triggers the thermal runaway and results in irreparable disaster during recycling. Chemical discharge is a common method to eliminate hazards by immersing batteries in an aqueous solution to release the remnant energy. However, a high-efficiency discharge solution usually causes severe corrosion of the battery shell, inducing safety accidents. In this work, theoretical and experimental studies are carried out in various solutions to investigate the efficiency and corrosion of chemical discharge strategy. The results suggest that zinc acetate solution is a potential discharge medium with excellent comprehensive properties compared with NaCl, MnSO4, FeSO4, and KAc solutions. Electrolytic reactions and external short circuit have been proved to be the essential causes of high discharge efficiency. Adsorption theory and Kolbe reaction are used to explain the low corrosion of battery shells in acetate solutions. Besides, the thermal stability of treated spent batteries also validates our discharge strategy's feasibility and ensures safety during transportation, storage, and recycling.