Efficient Recovery of Valuable Metals from Lithium-Ion Battery Cathodes Using Phytic Acid-Based Deep Eutectic Solvents at a Mild Temperature

Abstract

Recycling of waste lithium-ion batteries (LIBs) requires metal leaching from the LIB cathode; however, the metal-leaching process is too challenging to be efficient, green, and mild simultaneously. Moreover, the leaching efficiency at mild conditions by green solvents is not high and needs to be improved urgently. Here, deep eutectic solvents (DESs) composed of poly(ethylene glycol) 200 (PEG) and phytic acid (PHA) are designed to leach Co from LIB cathodes with an ultrahigh metalleaching efficiency of 0.987 at a low temperature of 80 °C for 24 h, which is much higher (ca. 0.3) than the efficiency of previously reported DESs. Moreover, the constituents (PEG and PHA) in DESs are low-cost, sustainable, and biodegradable; particularly, PHA is naturally available in legumes, cereals, dried fruits, vegetables, and other fruits, which are also edible by human beings. This work provides a super highly efficient, sustainable, and mild route for metal leaching from LIB cathodes.

Sustainable Tandem Strategy for Recycling the Lithium-Ion Battery Cathode and Treating Waste by Cheap and Biocompatible Deep Eutectic Solvents

“…PEG and PHA were mixed with the mole ratio of 1:1 to obtain DESs at 60 °C until the appearance of the liquid state, which was similar to the methods as previously reported. ,,− Magnetic adsorbents could be then synthesized by mixing DESs, Fe 3 O 4 , and LCO with a mass ratio of 1:5:0.1 at 100 °C for 24 h. A previous report suggested that PEG:PHA could dissolve LCO with high efficiency at a mild temperature; however, the leaching efficiency became lower as a result of the formation of the solid product when the temperature was not lower than 100 °C. The possible mechanism for the formation of magnetic adsorbent from DESs, Fe 3 O 4 , and LCO was the redox reaction between LCO and DESs, while Fe 3 O 4 plays the role of possessing magnetism.…”

“…Some DESs are reported to be unstable , and toxic; − instead, it could be overcome by applying the high tunability of DESs. Therefore, DESs have been applied in many fields, ,− including acting as green solvents for lithium-ion battery (LIB) dissolution and recovery. − …”

“…Namely, the magnetic adsorbent could be prepared by mixing DES polyethylene glycol:phytic acid (PEG:PHA), LIB cathode [i.e., lithium cobalt oxides (LCOs)], and ferroferric oxide (Fe 3 O 4 ) at a mild temperature; subsequently, the synthesized magnetic adsorbent could be used to remove organic dyes from wastewater and adsorb engine oil with high efficiency. PEG:PHA has been applied for LIB dissolution and physical property determination in previous reports. , Both PEG and PHA are cheap and biocompatible; furthermore, PHA mainly exists in whole grains, beans, and nuts. Moreover, the magnetic adsorbents after removing organic dye waste could be easily regenerated by a magnet.…”

Review of Ultrasound-Assisted Recycling and Utilization of Cathode Materials from Spent Lithium-Ion Batteries: State-of-the-Art and Outlook

“…In addition, microbial leaching is also a novel method for recovering cathode active substances, which has the benefits of low cost, reduced pollution, and high recyclability, and has become an important development direction of the recycling technology for valuable metals from SLIBs. , However, conventional biotechnology faces issues of a slow leaching rate, long leaching time, and difficulties in the selection and cultivation of microbial strains. , Ultrasound-assisted technology can increase the metal extraction efficiency of biolixiviation by increasing the yield of metabolites and enhancing mixing in the microscale . Therefore, ultrasound-assisted microbial leaching is also a promising alternative for the green recovery of valuable metals from SLIBs.…”

“…107,108 However, conventional biotechnology faces issues of a slow leaching rate, long leaching time, and difficulties in the selection and cultivation of microbial strains. 109,110 Ultrasound-assisted technology can increase the metal extraction efficiency of biolixiviation by increasing the yield of metabolites and enhancing mixing in the microscale. 111 Therefore, ultrasound-assisted microbial leaching is also a promising alternative for the green recovery of valuable metals from SLIBs.…”