Controlled carbothermic reduction for enhanced recovery of metals from spent lithium-ion batteries

In this study, a controlled carbothermic reduction followed by self-redox leaching process is developed for the stepwise recovery of metals from spent NCM battery. In the controlled carbothermic reduction step, the phase of the product can be precisely regulated simply by controlling the temperature and graphite dosage. In the self-redox leaching step, a redox reaction is carried out between Mn and Co in an H2SO4 solution, resulting in the reduction of Co(III) and Co(IV) to Co2+, and the Mn(II) is oxidized to MnO2 solid product for separation. Under the optimized conditions of H2SO4 concentration of 3 mol/L, leaching temperature of 85 °C, leaching time of 3 h, and liquid-solid ratio of 6 mL/g, the leaching efficiencies of Li, Ni, and Co reached remarkable levels of 99.2%, 98.9%, and 96.4%, respectively, while Mn mostly exists in the form of a solid phase, with a leaching efficiency of only 2.7%.