Comparative Assessment & Environmental Impacts of Lixiviants for Hydrometallurgical Lithium‐Ion Battery Recycling

The environmental impact of inorganic acids, organic acids, and DESs for industrial-scale LIB recycling is evaluated using life cycle analysis. While inorganic acids are efficient but hazardous, greener alternatives, e.g., DESs, require further optimization. These findings highlight solid-to-liquid ratio as a critical yet overlooked parameter and emphasize the need for DES reformulation to enhance their viability for large-scale application.

Abstract

Hydrometallurgy, owing to its simplicity and efficiency, has emerged as the most competent method for bulk Lithium-ion batteries (LIB) waste recycling. Current hydrometallurgical methods rely on three different classes of lixiviants, i.e., inorganic acids, organic acids, and deep eutectic solvents (DES). While inorganic acids show unmatched efficiency, their toxicity raises concerns over large-scale usage. Over the past decade, research on greener alternatives, e.g., organic acids and DESs, has made immense progress. The cradle-to-grave life cycle analysis of these lixiviants at an industrial scale is of utmost importance for the success of the recycling process. Here, we perform the overall impact analysis of representative lixiviants from each class based on their efficiencies and compare them on various sustainability parameters, e.g., climate change, eutrophication, and toxicity. The ramifications of each lixiviant system at an industrial scale, including their production, leaching and precipitation efficiencies under optimized conditions, and end-of-life treatments have been considered. The results highlight the importance of optimizing solid-to-liquid ratio to make recycling environmentally and economically viable, which is often ignored. These findings also underline the need for significant optimization of DES formulations to fully realize their potential at the industrial scales and several points toward this have been discussed.