Khan, Ahsan, Department of Chemical Engineering, Bucknell University, One dent drive, Lewisburg, PA, 17837, ak062@bucknell.edu; Okolie, Jude, Department of Chemical Engineering, Bucknell University, Dana 212, One dent drive, Lewisburg, PA, 17837, jao020@bucknell.edu.
Lithium-ion batteries are promising alternatives to conventional energy sources, but repeated charge discharge cycling limits their service life. At end of life, cells are often deactivated by discharging in aqueous sodium chloride (NaCl), a simple and low-cost method. However, chloride ions accelerate corrosion of copper and aluminum current collectors and promote transition-metal leaching from cathodes, posing environmental risks. This study explores corrosion-mitigation strategies that maintain discharge performance while reducing metal loss. Cylindrical Li-ion cells were discharged in NaCl containing Na2SO3, glycerol, or TEA, and in chloride-free or inhibitor-modified electrolytes. In NaCl media, Na2SO3 scavenged dissolved oxygen, glycerol reduced water activity and formed diffusion-limiting films, and TEA acted as an organic film-forming inhibitor, together minimizing corrosion of steel, Cu, and Al. Chloride-free solutions 3 wt% Na2SO4 with 0.3 wt% NaHCO3, 3 wt% Na2SO4 in water-glycerol and water-ethanol, and 3 wt% Na2SO4 with 5 wt% reline were also evaluated, along with a two-step discharge sequence (20 wt% NaCl in first step and 3 wt% Na2SO4 with 0.3 wt% NaHCO3 in second step). Voltage drops were recorded over 30 hours, and post-discharge electrolytes were analyzed by ICP-MES for Cu, Al, Ni, Co, and Mn. Relative to NaCl, sulfate-based electrolytes such as Na2SO4 and NaHCO3 are expected to reduce metal dissolution by limiting chloride activity and promoting protective surface films. Mixed-solvent sulfates should further suppress corrosion through decreased ionic mobility and improved inhibitor interaction. In contrast, baseline NaCl is anticipated to cause rapid Cu dissolution and visible deposits, while the addition of TEA or Na2SO3 may partially mitigate chloride-induced pitting. Overall, this study highlights those electrolytes that are chosen to balance inhibitor chemistry, conductivity, and corrosion protection, enabling safer and more efficient battery deactivation with reduced environmental impact.
Lithium-ion batteries, discharging, inhibitors,