Separation of Cobalt from Nickel from NMC battery cathodes using Phosphonium based Ionic Liquids.
An?ela KOVA?EVI?1, Martina SANADAR1, Marilena TOLAZZI1, Andrea MELCHIOR1
1University of Udine, Udine, Italy
Cobalt, one of the main components of cathode used in Li ion battery is reported on the 2020 list of critical raw materials. In 2030, the demand for cobalt will increase five times compared to the current supply of this element. The demand is highly driven by the transition to electrical mobility approach that intends to take over the current internal combustion engine vehicles with the more environmentally friendly EVs. Recycling and reusing end – of – life materials is another approach for sustainable development of new batteries. LIBs recycling boost energy consumption and CO2 emissions reduction, saves natural resources avoiding raw materials mining and importing. Current hydrometallurgical processes for the recovery of the Co2+ ions from aqueous solutions have some interesting advantages (low energy consumption, process flexibility, higher purity), but require the use of significant amounts of toxic volatile organic compounds (VOCs) in the solvent extraction stages and of multiple extracting ligands to separate the different metals present in the leachates. Ionic liquids (ILs) have many potential applications. They are powerful solvents with many advantages such as negligible vapor pressure, non-toxicity, reusability, and high thermal stability. Most commonly used hydrophobic ILs are are Aliquat (nitrogen-based IL) and Cyphos® (phosphonium based). In comparison to the nitrogen-based ILs, phosphonium-based ILs possess higher thermal stability and are more stable in strong basic media due to the absence of acidic proton. Most leaching processes, at least for nickel laterites and sulfides, extract both cobalt, nickel and result in a mixed Co/Ni solution that needs to be separated. This work focuses on the improved process of cobalt/nickel separation recovery from lithium-ion batteries (LIBs) lithium nickel manganese cobalt oxide (NMC) cathode waste materials by using hydrometallurgical methods. More environmentally friendly IL with decanoate anion (Dec) was compared with two IL with halogen contra-anion; chloride (Cl-) and bromide (Br-) whose efficiency is already proven. Furthermore, extraction enthalpy in IL with decanoate was determined. In the acid leaching step, the effects of acid concentration, H2O2 concentration and leaching time with the leaching percentage were investigated. To complete the recovery process, further separation was proposed using three phosphonium based IL-s; trihexlytetradecylphosphonium chloride (P66614) (Cl), bromide (P66614) (Br) and decanoate, (P66614) (Dec). Acid concentration in water media and timing for extraction was tested. After extraction, the water phase was measured by ICP-OES to quantitatively determine metal concentrations. UV-Vis spectroscopy was used for spectral observation of IL phase. Lastly, extraction enthalpy in (P66614) (Dec) was determined by Isothermal Titration Calorimetry (ITC).