A Weak Acidic and Strong Coordinated Deep Eutectic Solvent for Recycling of Cathode from Spent Lithium‐Ion Batteries

Abstract

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.

Carbon neutrality strategies for sustainable batteries: from structure, recycling, and properties to applications

“…Therefore, various auxiliary means to achieve rapid dissolution of cathode materials have been reported, such as mechanochemical activation, 109,152,179,180 ultrasound assisted, 145,[181][182][183] and deep eutectic solvent. 106,[184][185][186][187] Mechanochemical activation affects the physicochemical properties of the cathode material to improve the leaching efficiency of metal ions. The activated cathode powder shows a decrease in grain size, increase in specific surface area and appearance of mesoporous structure.…”

A Novel Green Process for Recovery of Transition Metal Ions from Used Lithium-ion Batteries by Selective Coordination of Ethanol

“…The DES-based leaching process can achieve selective separation by changing the metal ion coordination environment. 7,25,26 This method allows the recovery of metal ions without solvent extraction, giving it a great advantage in green processes. 27,28 A comparative flow diagram of the conventional recovery process and selective coordination separation process is shown in Figure 1.…”

“…T peak , which is the temperature with the maximum degradation rate, can be obtained from the thermogravimetric differential (DTG) curve (a curve in which the points on the TG curve are differentiated once with respect to the time coordinate). 26 Theoretically, it is necessary to control the reaction temper-ature using a BeCl/LA DES. This can provide guidance for subsequent leaching experiments.…”

“…The characteristic peaks at 1737.9 and 1591.3 cm −1 are the stretching vibration peaks of −COO−, which are in accordance with [Co(C 2 H 5 O) 6 ](C 3 H 6 O 3 ) 2 . 26 XPS analysis revealed the components of the precipitated products. Figure .…”

“…The ILs and DESs are eco-friendly solvents with low volatility and biodegradability properties that can reduce wastewater discharge and avoid secondary contamination. , Another strategy for improving the recovery process is selective separation. The DES-based leaching process can achieve selective separation by changing the metal ion coordination environment. ,, This method allows the recovery of metal ions without solvent extraction, giving it a great advantage in green processes. , A comparative flow diagram of the conventional recovery process and selective coordination separation process is shown in Figure .…”