Separation of metals from acetic acid leaching solution of spent lithium-ion batteries by ionic liquid system

Abstract

Spent Li-ion batteries (LIBs) pollute the environment and endanger human health; however, they are valuable mineral resources. Here, we designed an extraction system composed of 0.4 mol/L 2-thenoyltrifluoroacetone (HTTA), 0.4 mol/L trioctylphosphine oxide (TOPO), and ionic liquid (IL) 1-Butyl-3-MethylImidazolium bis (trifluoromethyl sulfonyl) imide to recover valuable metals from spent LIBs. Under the optimum conditions (O/A = 1/1, 25 °C, reaction time 20 min, and pH = 3.65, the pH of the solution does not need to be adjusted), over 99.54% of Co, 99.85% of Mn, and 99.68% of Ni were extracted, while only 2.84% of Li were coextracted. The ultraviolet spectrum analysis showed that the spectral peaks of the stripping solution changed at 266 and 293 nm, indicating that CH3COO– participated in the extraction reaction. Following stripping with sulfuric acid, the pH of the solution was adjusted with 2.0 mol/L NaOH, and approximately 99% of the Al3+ ions were precipitated. Nickel and manganese sulphates were added to the stripping solution. The precursor was prepared using a coprecipitation method. The precursor was then mixed with lithium hydroxide and calcined at 1000 °C for 12 h to obtain LiNi1/3Co1/3Mn1/3O2.