Green recycling of valuable metals from spent cathode materials by water electrolysis

Conventional methods of recycling spent lithium-ion batteries (LIBs) consume large amounts of acid and base during the hydrometallurgical process. Herein, we proposed an efficient process to recover valuable metals from spent LIBs based on water electrolysis, without consuming external acids and bases. With the help of thermal reduction pretreatment, the cathode material can be converted into acid-soluble components of Ni, Co, NiO, CoO, MnO and Li2CO3. During the water electrolysis process, H+ and OH- are generated in the anode cell and cathode cell respectively, which synchronically achieves the leaching of valuable metals and the precipitation of transition metal ions in the two separated cells. Under the optimum electrolysis conditions, 84.3% Ni, 82.6% Co and 74.1% Mn and 100% Li were leached, meanwhile, more than 99% of transition metals in the leachate were precipitated. After filtration, Li+ was precipitated into Li2CO3 by adding Na2CO3, and the Na2SO4 was recovered and reused as the electrolyte by evaporative crystallization. Finally, the recovered ternary precursors and Li2CO3 can be used as raw materials for regenerating a new cathode material. Additionally, this metal recovery system avoids membrane blockage and the interaction of products between cathode and anode cells, hence improving the efficiency of metal leaching and precipitation. The whole process provides a green method for recovering valuable metals from spent LIBs with the minimum chemical consumption and emission.