Response Surface Methodology (RSM) Design to Optimize the Cathode of Li-Ions Batteries Recycling in Deep Eutectic Solvent and DFT Simulation

Abstract

In this study, the dissolution of a cathode of Li-ion batteries (CLIB) in a deep eutectic solvent (DES) composed of choline chloride (ChCl) and glucose (G) was investigated using the response surface methodology (RSM) experimental design. The temperature ranged from 45 to 105 °C, time from 2 to 26 h, agitation from 250 to 850 rpm, and DES/CLIB ratio from 20 to 100 g/g. According to the analysis of variance (ANOVA), temperature had the most significant impact on the dissolution of all elements (Ni, Co, Mn, and Li). In contrast, agitation had no significant effect on metal recovery. Under optimal conditions, including a temperature of 93 °C, a time of 20 h, an agitation of 550 rpm, and a DES/CLIB ratio of 80 g/g, the efficiencies of Ni, Co, Mn, and Li were 85.7%, 90.1%, 89.6%, and 93.2%, respectively, which matched well with the modeling results. This paper presents a comprehensive DFT investigation at the B3LYP/6-31G(d) level of theory on the behavior of transition metal cations in the presence of ChCl and G. Findings elucidate the preference of specific cations for particular ligands, the stability of complex formations, and the crucial role of ligands in electron transfer processes.