Mechanistic Study of Lithium-Ion Battery Cathode Recycling Using Deep Eutectic Solvents

Abstract

The colossal increase in the use of Lithium-ion batteries (LiBs) necessitates their efficient recycling to ensure a steady supply of essential cathode materials, e.g., Li, Co, and Ni, as well as to tackle huge bulks of battery waste. Deep Eutectic Solvents (DESs) are green solvents with immense potential in the hydrometallurgical recycling of LiB cathodes, although their leaching mechanism has not been explored. We investigate the leaching mechanism of the different transition metals (TM), e.g., Co, Ni, and Li, from the most abundantly used LiB cathode materials NMC and NCA in an ethylene glycol (EG):choline chloride(ChCl) based DES. Leaching experiments performed by altering different parameters and density functional theory (DFT) calculations imply that EG participates in H-bonding and weakens the metal−oxygen bond of the TMs, whereas Cl − attacks the metal center to form chlorometalate complexes. Li on the other hand is surrounded by Cl − ions and leached in the solution. The increased concentration of ChCl in DES ensures the facile formation of these complexes and enhances leaching.

Selective Extraction of Critical Metals from Spent Li‐Ion Battery Cathode: Cation–Anion Coordination and Anti‐Solvent Crystallization

“…FTIR findings evidenced no meaningful structural change in functional groups of DES after three times of reuse, confirming reusability of DES. 13 C-NMR confirmed structural evolution of DES during leaching (Figure S19, Supporting Information). A direct comparison with the original DES established an upfield shift in the carboxyl group of acetic acid during repetitive leaching, evidencing consumption of acetic acid during leaching; whilst, the structure of ChCl remained stable.…”

“…[ 12 ] For example, Luo et al and Alhashim et al explained the coordination of Cl − with transition metals based on frontier orbital theory, molecular electrostatic potential, and ab initio molecular dynamics simulations. [ 13 ] However, despite consumption of HBD as an oxygen acceptor during leaching, HBD will remain in DES and not be completely consumed. These coordination structures of the remaining HBD with transition metals and Li have been overlooked in the past.…”

Realizing Lean-Leachate Recycling of Spent Lithium Nickel Oxides by Dynamically Stabilizing the Hole-Mediated Diffusion Kinetics

“…The recovery rate (99.73%) of lithium is slightly higher compared to nickel. This could be attributed to the smaller radius of Li ions and their weaker electrostatic adsorption forces, making the elution easier . Theoretically, the adsorption of the elements by the GO phase is driven by the existence of a concentration gradient.…”

A systematic review of efficient recycling for the cathode materials of spent lithium-ion batteries: process intensification technologies beyond traditional methods

“…After leaching, the metal ions can be recovered from the leachate through electrodeposition, chemical precipitation, or further extraction. 135…”