Recommended Practices for the Electrochemical Recovery of Cobalt from Lithium Cobalt Oxide: A Case Study of the Choline Chloride:Ethylene Glycol Deep Eutectic Solvent

Mohamed Shahid; Suchithra Ashoka Sahadevan; Vijay Ramani; Shrihari Sankarasubramanian

doi:10.1002/cssc.202401205

Recommended Practices for the Electrochemical Recovery of Cobalt from Lithium Cobalt Oxide: A Case Study of the Choline Chloride:Ethylene Glycol Deep Eutectic Solvent

ChemSusChem. 2024 Aug 30:e202401205. doi: 10.1002/cssc.202401205. Online ahead of print.

Authors

Mohamed Shahid^{1

2}, Suchithra Ashoka Sahadevan³, Vijay Ramani³, Shrihari Sankarasubramanian^{1

4}

Affiliations

¹ Department of Biomedical Engineering and Chemical Engineering, University of Texas at San Antonio, San Antonio, TX 78249, USA.
² Department of Chemical Engineering, University of Petroleum and Energy Studies, Dehradun, 248007, India.
³ Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, Missouri, USA.
⁴ Department of Mechanical Engineering, University of Texas at San Antonio, San Antonio, TX 78249, USA.

PMID: 39213259
DOI: 10.1002/cssc.202401205

Abstract

We recommend best practices for the recovery of cobalt from LiCoO₂ (LCO) lithium-ion battery (LIB) cathodes by (i) leaching using green deep eutectic solvents (DES) and (ii) subsequent electrodeposition, through a case study of the choline chloride (ChCl):ethylene glycol (EG) DES. DES physical properties (conductivity, viscosity, and surface tension) were tailored by varying the composition between mole ratios of 1 : 2 and 1 : 5 (ChCl:EG). Examined along with leaching process parameters (temperature, duration), increasing the fraction of hydrogen bond donors (HBDs) decreased DES surface tension and enhanced leaching. Complete Co recovery was achieved using 1 : 5 ChCl:EG DES at 160 °C and 48 h. Leaching temperatures >160 °C are discouraged due to DES thermal degradation. The electrodeposition process was optimized for selective Co recovery with high faradaic efficiency. The leaching ability of the DES was antithetical to the stability of electrodeposition cell components and required operational parameter adjustment to minimize degradation. The optimized system (copper cathode and stainless-steel anode) employing 1 : 5 DES leachate exhibited a faradaic efficiency of ~80 %, specific Co recovery of ~0.8 mg hr^<M-1 cm^-1 at 50 °C and evidence of uniform deposition. DES surface tension is a key descriptor of metal recovery, and guidelines are presented to maximize selective Co recovery.

Keywords: Cobalt; Deep eutectic solvents; Electrodeposition.; Lithium-ion battery; Recycling.