An environmentally friendly discharge technology to pretreat spent lithium-ion batteries

Lithium-ion batteries have been widely used in electronic products. However, disposal of these spent LIBs containing heavy metals will result in environmental pollution. Therefore, the recycling of spent LIBs has become highly desirable from the perspective of both resource conservation and environmental protection. Discharging is an essential pre-treatment to decrease the risk of following process, such as dismantling or crushing. Taking both discharge efficiency and environmental impact into account, this work analyzed the discharge process of both chemical and physical discharging systematically. Different solutions and conductive metal powder were evaluated according to their discharge efficiency and stability. The gaseous, liquid, and solid pollutants from discharge process were analyzed qualitatively and quantitatively. FeSO4 solution turned out to be the most environmentally friendly among NaCl solution and MnSO4 solution. Large-scale discharge models were designed based on the results. The quick discharge model using FeSO4 solution reduces the residual voltage to 1.0 V within 125 min; the full discharge model using both NaCl solution and FeSO4 solution reduces the residual voltage to 0.5 V or lower within 183 min.