Choline chloride–ethylene glycol based deep-eutectic solvents as lixiviants for cobalt recovery from lithium-ion battery cathode materials: are these solvents really green in high-temperature processes?

Peeters, Nand; Janssens, Karl; Vos, Dirk De; Binnemans, Koen; Riaño, Sofía

doi:10.1039/d2gc02075k

Cited by 47 publications

(43 citation statements)

References 64 publications

(126 reference statements)

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“…This can be attributed to the Cl − attack on the TM center, as has been observed in other ChClbased DES systems. 23 The UV spectra of the reaction mixture comprising DES-3 and NMC/NCA at 180 °C are recorded at As expected, in both cases, we observe the increase in the intensity of the absorbance peaks with time. The peaks at 614 nm can be attributed to octahedral cobalt complexes that may contain different ligands in their coordination sphere including chloride.…”

Section: ■ Results and Discussionsupporting

confidence: 78%

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

Alhashim

Bhattacharyya

Tromer

et al. 2023

ACS Sustainable Chem. Eng.

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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.

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Section: ■ Results and Discussionsupporting

confidence: 78%

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

Alhashim

Bhattacharyya

Tromer

et al. 2023

ACS Sustainable Chem. Eng.

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“…Thus, cobalt(III) could be reduced by water evolving during the dissolution reaction. Also, the formation of chlorine was reported upon the dissolution of lithium‐ion battery cathode materials in different chloride‐containing DESs, indicating chloride oxidation by cobalt(III) [22,26,27,35,36] . Meng, Guo et al.…”

Section: Resultsmentioning

confidence: 99%

“…The precipitates are suitable reagents for the production of new lithium‐ion battery cathodes [23,27,33] . Although several investigations show, that the DES can be reused for up to five times, [29,31,35] other publications raise considerable doubts regarding their stability [20,21,27,36] . For example, in DESs consisting of a carboxylic acid and an alcohol, up to 35 % of both components appear to be present in an esterified form even at room temperature [37] .…”

Section: Introductionmentioning

confidence: 99%

Cobalt Deposition from Ionothermally Dissolved Cobalt Oxides

2023

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Owing to the environmental problems of numerous metal production processes, there is a growing need for more energyefficient approaches. Cobalt is considered a strategic element that is extracted not only from ores but also from spent Li-ion batteries. One promising new approach is ionometallurgy, which is the extraction of metal oxides by ionic liquids (ILs). This study concerns new investigations into ionometallurgical processing of CoO, Co 3 O 4 , and LiCoO 2 in the IL betainium bis(trifluoromethylsulfonyl)imide, [Hbet][NTf 2 ]. Three crystal structures of cobaltÀ betaine complex compounds and combined spectroscopic and diffraction studies provide insights into the dissolution process. In addition, an optimized dissolution procedure for metal oxides is presented, avoiding the previously reported decomposition of the IL. Subsequent cobalt electrodeposition is only possible from cationic complex species, highlighting the importance of a thorough understanding of the complex equilibria. The presented method is also compared to other recently reported approaches.

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“…Surprisingly, the green character of the DES is highlighted in this application [32,35,88]. However, recent research in Binnemans' group has shown that this DES is not thermally stable at such elevated temperatures and that even toxic decomposition products, such as trimethylamine or 2-chloroethanol, are formed [89].…”

Section: Limited Chemical Stabilitymentioning

confidence: 99%

Ionic Liquids and Deep-Eutectic Solvents in Extractive Metallurgy: Mismatch Between Academic Research and Industrial Applicability

Binnemans

Jones

2023

J. Sustain. Metall.

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The past 10–20 years have seen numerous academic papers describing the benefits of ionic liquids (ILs) and deep-eutectic solvents (DESs) for leaching, solvent extraction and electrowinning. The scientific community—including the authors of this opinion article—have frequently proclaimed these neoteric solvents as game-changers in extractive metallurgy. Despite this, there have been no commercial breakthroughs. In this paper we reflect on the reasons why ILs and DESs seem to have failed to impact on the metallurgical industry. These include: (1) issues with high viscosity; (2) limited chemical stability under the conditions of metallurgical processes; (3) difficulties with recycling and reuse; (4) a lack of demonstrated unit processes and flowsheets on the pilot scale; (5) insufficient material-property data available for engineering purposes; (6) the administrative burden of obtaining licenses and safety permits; (7) very high costs for large-scale operations; and (8) minimal added value compared to state-of-the-art hydrometallurgical processes. Our belief is that innovations in hydrometallurgy based on ILs or DESs are unlikely. Instead, we should be aiming for a deeper understanding of hydrometallurgical processes at the molecular level. This is because advances are more likely to derive from the refocused efforts of experienced IL/DES researchers investigating the speciation and chemical thermodynamics of hydrometallurgical solutions, which will then hasten the transition from linear to low-energy-input, circular hydrometallurgy. Graphical Abstract

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Choline chloride–ethylene glycol based deep-eutectic solvents as lixiviants for cobalt recovery from lithium-ion battery cathode materials: are these solvents really green in high-temperature processes?

Abstract: The thermal decomposition of the choline chloride–ethylene glycol (ChCl : EG) deep-eutectic solvent (DES) is studied during the leaching of lithium cobalt oxide (LiCoO2) at 180 °C.

Cited by 47 publications

References 64 publications

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

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

Cobalt Deposition from Ionothermally Dissolved Cobalt Oxides

Ionic Liquids and Deep-Eutectic Solvents in Extractive Metallurgy: Mismatch Between Academic Research and Industrial Applicability

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