Effect of graphite on selective lithium recovery from NCM-lithium battery black mass via hydrogen reduction

The recovery of lithium from spent ternary lithium-ion batteries holds significant potential for alleviating environmental pressures and minimizing lithium waste. Hydrogen reduction for lithium extraction has been extensively studied, but primarily focused on cathode materials alone. Industrially, however, spent lithium batteries yield mixed cathode-anode waste. Notably, hydrogen reduction in the presence of anode graphite has not been previously investigated. This study explores the feasibility and advantages of preferential lithium extraction via hydrogen reduction treatment of mixed cathode and anode materials from spent ternary lithium-ion batteries. The critical temperature was identified to be 500 °C. Below 500 °C, hydrogen reduction predominates, while above 500 °C, carbon reduction gradually takes over. Under optimal conditions (T = 500 °C,t = 60 min,Q = 150 mL/min), the cathode materials were reduced to a mixture of LiOH, Co, Ni, and MnO. Subsequent water leaching achieved a high lithium recovery efficiency of 92.02 %. Furthermore, most metallic elements in the residue were reduced to their lowest oxidation states, facilitating their potential recovery via multi-stage leaching processes. This study demonstrates the successful recovery of lithium through hydrogen reduction in the presence of anode graphite, offering a theoretical basis for industrial production.