The leaching and recycling of valuable metals via environmentally benign solvents is important because of the everincreasing waste lithium-ion batteries, but it remains a challenge. Herein, a multi-functional deep eutectic solvent (DES) based on lactic acid (LA) and guanidine hydrochloride (GHC) was used to extract cobalt and lithium ions from LiCoO 2 . Due to the strong acidity (protons) and abundant chlorine coordinating ions of LA/GHC, the solubility of LiCoO 2 in LA/GHC could reach as high as 19.9 mg g À 1 (stirred at 80 °C for 24 h), and a little LiCoO 2 powder even could be dissolved at room temperature without stirring. Oxalic acid was used to strip and separate the oxalates of cobalt and lithium. Furthermore, LA/ GHC could be recycled with a similar dissolving performance. This work avoided using corrosive acids and could be realized at low temperature (80 °C), making it energy-saving and costeffective. It shows DESs have great potential in extracting strategically important metals from LiCoO 2 cathodes and provides an efficient and green alternative for sustainable recycling of spent lithium-ion batteries.
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.
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