Thorpe, Noah, Chemical Engineering, Bucknell University, 173 Hubbard Street, Concord, MA, 01742, net008@bucknell.edu; Okolie, Jude, A, Chemical Engineering, Bucknell University.
Lithium-based batteries are increasingly replacing traditional battery technologies, leading to a growing accumulation of spent lithium batteries. These used batteries contain valuable heavy metals that can be recovered through various recycling methods. However, due to their residual voltage, they must first be safely discharged before dismantling can occur. This research investigates optimal solvents for discharging lithium-based batteries to a safe voltage level for handling and recycling. Additionally, the study evaluates the environmental impact of the discharging process, with a focus on potential pollution risks if the resulting waste enters the environment without further treatment. Analytical techniques included ICP-MS and GC-MS for waste liquid analysis, and XRD and SEM-EDS for waste solid characterization. Three solvents were tested: sodium chloride (NaCl), sodium sulfate (Na₂SO₄), and iron sulfate (FeSO₄). These solvents were chosen because of their high electrical conductivity in aqueous solution. NaCl had the highest discharge efficiency, nearly 40%, and consistently reduced the batteries to a relative voltage of about one volt. At this voltage, the batteries can be safely dismantled, allowing the heavy metals to be recycled. Preliminary results show that NaCl produced the highest heavy metal ion concentrations, with nickel, lithium, and magnesium being the most abundant. Na₂SO₄ produced lower concentrations overall but still showed elevated levels of nickel, copper, and zinc. GC-MS analysis confirmed that none of the solvents caused leakage of volatile organic compounds. Waste solid characterization revealed that sodium chloride use leads to precipitates of iron oxide (Fe₂O₃) and some unreacted NaCl. Sodium sulfate use results in the formation of solid copper sulfate (CuSO₄). Although no volatile organic compounds were detected, the high heavy metal concentrations and precipitate formation indicate that the waste could cause significant environmental pollution if not treated further.