Leaching Metal Elements from Lithium Cobalt Oxide in an Alcohol-Carboxylic Acid Non-Aqueous System.

The leaching of spent lithium-ion battery (LIBs) cathode materials with non-aqueous systems has received widespread attention. In this paper, a binary non-aqueous system of glycerin(Gly)-formic acid(FA)and a ternary non-aqueous system of Gly-FA-choline chloride (ChCl) were used for the leaching of LiCoO₂ cathode materials. The effects of leaching time, leaching temperature and liquid-to-solid ratio conditions on leaching rates were investigated. The results indicated that the addition of ChCl was able to significantly improve the leaching rates of the metals. Under the optimal conditions of time 210 min, temperature 120 °C and liquid-solid ratio 100 mL/g, the ternary non-aqueous system achieved leaching efficiencies of 99.77% and 89.09% for Li and Co respectively, higher than the 67.94% and 67.11% for the binary non-aqueous system. The leachate was analyzed by UV-Vis and FT-IR spectroscopy to reveal the leaching mechanism. The results showed that FA was able to reduce Co³⁺ to Co²⁺ in LiCoO₂. However, Co²⁺ was present in different forms in the two non-aqueous systems, where the binary system was present as a hexa-coordination and the ternary system as a tetra-coordination. [ABSTRACT FROM AUTHOR]