Experimental and DFT simulation of collective dissolution of anode/cathode of Li−ion batteries using a ChCl−PTSA deep eutectic solvent--颗粒学报PARTICUOLOGY

Karimi, S., & Behnajady, B. (2025). Experimental and DFT simulation of collective dissolution of anode/cathode of Li−ion batteries using a ChCl−PTSA deep eutectic solvent. Particuology, 103, 217-231. https://doi.org/10.1016/j.partic.2025.05.020

Experimental and DFT simulation of collective dissolution of anode/cathode of Li−ion batteries using a ChCl−PTSA deep eutectic solvent

Saeid Karimi^a *, Bahram Behnajady^b

a Department of Metallurgy and Materials Engineering, Hamedan University of Technology, Hamedan, 65169-13733, Iran
b Advanced Materials Research Institute, Faculty of Materials Engineering, Sahand University of Technology, Sahand New Town, Tabriz, 5331817634, Iran

10.1016/j.partic.2025.05.020

Volume 103, August 2025, Pages 217-231

Received 12 April 2025, Revised 16 May 2025, Accepted 23 May 2025, Available online 31 May 2025, Version of Record 10 June 2025.

E-mail: s.karimi@hut.ac.ir; karimi6439@gmail.com

Highlights

• ChCl-PTSA DES was successfully used for the leaching of LIB A/C.

• Ni, Co, Li, Mn, and Cu dissolved with over 90 % efficiency at 100 °C and 24 h.

• XRD and SEM analyses confirmed the presence of graphite in the leaching residue.

• DFT analysis showed that hydrogen bonding plays a crucial role in the formation of the DES.

• Cu(I), Co(II), and Mn(II) exhibit enhanced stability in the DES system due to high HOMO-LUMO gaps.

Abstract

In this study, the cumulative dissolution of the anode and cathode (A/C) mixture of Li-ion batteries (LIBs) in a deep eutectic solvent (DES) composed of choline chloride (ChCl) and p-toluenesulfonic acid (PTSA) was evaluated within a temperature range of 40–100 °C and a time range of 20–1440 min. The results showed that Ni, Co, Li, Mn, and Cu metals dissolved with over 90 % efficiency at 100 °C and 1440 min, while Al dissolved at only about 26 % under the same conditions. XRD and SEM-EDS analyses confirmed these findings, with minimum residual compounds of Ni, Co, Li, Mn, or Cu detected. FTIR confirmed ChCl−PTSA DES formation and its after-leaching stability, allowing reuse with minimal changes for sustainable metal recovery. The ChCl–PTSA DES exhibits a symmetric σ−profile (centered at σ = 0 ± 0.2 e/Å²), COSMO-identified nucleophilic/electrophilic regions (+0.214 to −0.158 e/Å²), and Mulliken charges (O: −0.47 to −0.65, Cl: −0.39, H: +0.06 to 0.15). These density functional theory (DFT) simulations highlight charge complementarity, stabilizing the eutectic structure via sulfonic oxygen, chloride, and ammonium group interactions. According to DFT simulation for pure and containing metal ions DES, the ChCl−PTSA exhibits a 3.87 eV HOMO−LUMO gap, enabling efficient metal leaching. Co(II) (2.29 eV gap) and Mn(II) (0.56 eV) show higher stability than higher oxidation states, while Li(I) widens the gap (3.97 eV), enhancing stability. DFT simulations reveal distinct COSMO surface charge distributions for metal ions in ChCl–PTSA, categorized as: (1) highly polarized (Co(II): +0.3253 to −0.2158 e/Å²; Mn(II): +0.3769 to −0.2496 e/Å²), exhibiting strong charge separation and high reactivity; (2) moderately polarized (Ni(II): +0.2240 to −0.2061 e/Å²; Al(III): +0.2547 to −0.2192 e/Å²), balancing reactivity and stability; and (3) minimally perturbed (Li(I): +0.2485 to −0.1861 e/Å²; Cu(I): +0.3233 to −0.1876 e/Å²), showing stable charge delocalization.

Graphical abstract

Keywords

Li-ion batteries (LIBs); p-toluenesulfonic acid; Cumulative leaching; Deep eutectic solvent (DES)

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