Analyzing the environmental impact of recovering critical materials from spent lithium-ion batteries through statistical optimization

Abstract

The exponential growth of the lithium-ion battery industry has heightened interest in recycling critical metals such as lithium, manganese, cobalt, and nickel. This research focused on optimizing the leaching process parameters using inorganic acids (HCl, HNO3, and H2SO4) to recover these elements from cathode powders via hydrometallurgy. A statistical tool was utilized to optimize several parameters, including temperature, leaching time, the concentration of acids, solid-to-liquid ratio, and % volume of H2O2, to achieve the highest recovery percentage for critical metals. To evaluate the environmental impact of optimized processes at the laboratory scale, this study proposed a novel scheme that integrates the Design of Experiments and Life Cycle Assessment methodologies. Sulfuric acid was identified as the best inorganic acid for recovering critical materials from NMC 532 cathode powder, with all optimized conditions for each acid showing better environmental performance than those found in the literature. This research provides significant preliminary insights into the sustainability assessment of metal recovery from spent lithium-ion batteries. The proposed environmental impact methodology can be expanded to larger system boundaries of laboratory-scale processes, providing a comprehensive framework for assessing the environmental impact of metal recovery from spent lithium-ion batteries.