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 metal-leaching 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.