Upcycling of cathode materials from spent lithium-ion batteries cathode materials enabled by deep eutectic solvent

Deep Eutectic Solvents (DES) represent a promising class of environmentally friendly solvents with potential applications in battery recycling. Nevertheless, there exists a paucity of research regarding the regeneration of layered cathode materials from DES leachates. Therefore, this study introduces a method for the recovery and regeneration of high-capacity layered cathode materials using an ethylene glycol (EG)/citric acid (CA)-based DES (e.g., EG:CA = 9:1 in molar ratio). The experimental results show that the leaching efficiencies of Li, Ni, Co, and Mn can reach 98 %, under the leaching condition of (i) a reaction temperature of 90 °C, (ii) a Solid/Liquid ratio of 20 g L-1, (iii) EG:CA with a molar ratio of 9:1 and (iv) a reaction time of 300 min. The kinetics of the leaching process show that the leaching is controlled by a surface chemical reaction. The Li1.2Mn0.54Ni0.13Co0.13O2 material was regenerated from the leachate using the sol-gel method. The regenerating temperature significantly influences the material's performance. Under the optimal conditions, the regenerated material demonstrates a capacity of 273.8 mAh·g-1. This study introduces a novel approach for regenerating lithium-rich layered cathode materials through the utilization of DES, providing valuable insights into the recycling and regeneration of spent batteries.