Recovery of Lithium and Cobalt from Spent Lithium-ion Battery Cathode Material Using Deep Eutectic Solvents

Abstract

The increasing demand for portable electronics and electric vehicles stresses the urgent need for sustainable solutions to recycle spent lithium-ion batteries (LIBs). This study introduces a computational-experimental framework to develop deep eutectic solvents (DESs) optimized for recycling LIB cathodes. The study used the conductor-like screening model for real solvents (COSMO-RS) modeling, machine learning (ML) prediction, density functional theory (DFT) calculations, and experimental validation for lithium and cobalt recovery from lithium cobalt oxide cathode material. In COSMO-RS prediction, 675 potential DES combinations were computationally screened to identify high-performing candidates. Eight promising DESs, composed of green, biocompatible materials such as glycine, betaine, carnitine, ascorbic acid, and citric acid, were synthesized and evaluated experimentally. Among the synthesized DESs, the glycine, ascorbic acid, water (G: A: W) composition demonstrated superior performance in leaching experiments. A general factorial design was used to identify the optimum experimental conditions. The novel DES achieved an exceptional leaching efficiency of 99.1% for Li and 97.9% for Co at 80℃ and 2hrs conditions. The ensemble neural network among the different tested ML algorithms predicted the leaching efficiencies quantitatively with R2>0.95. The ML method facilitated precise optimization of process parameters such as temperature, DES composition, and reaction time. Extraction kinetics analysis revealed activation energies of 110.9 kJ/mol for lithium and 81.5 kJ/mol for cobalt and established an endothermic surface reaction leaching mechanism. DFT calculations further elucidated the molecular interactions driving metal extraction. The calculation showed hydrogen bonding and van der waal accounted for more than 90% of the interaction energy of the leaching process. Additionally, the DES demonstrated high recyclability over seven cycles, while producing high-purity lithium oxalate and cobalt oxalate. This approach facilitated the selective recovery of high-purity lithium and cobalt in oxalate form. Lastly, economic analysis of the studied DES reveals a profit of $8660.5 for 1 ton of LCO battery recycled per year. The novel DES shows significant promise as an eco-friendly and efficient alternative for metal recovery in hydrometallurgical processes.

Date of Award	14 Dec 2024
Original language	American English
Supervisor	ENAS NASHEF (Supervisor)