Electrochemical process for recovery of metallic Mn from waste LiMn₂O₄-based Li-ion batteries in NaCl−CaCl₂ melts

A new method is proposed for the recovery of Mn via the direct electrochemical reduction of LiMn₂O₄ from the waste of lithium-ion batteries in NaCl−CaCl₂ melts at 750°C. The results show that the LiMn₂O₄ reduction process by the electrochemical method on the coated electrode surface occurs in three steps: Mn(IV) → Mn(III) → Mn(II) → Mn. The products of this electro-deoxidation are CaMn₂O₄, MnO, (MnO)_x(CaO)_1−x, and Mn. Metal Mn appears when the electrolytic voltage increases to 2.6 V, which indicates that increasing the voltage may promote the deoxidation reaction process. With the advancement of the three-phase interline (3PI), electric deoxygenation gradually proceeds from the outer area of the crucible to the core. At high voltage, the kinetic process of the reduction reaction is accelerated, which generates double 3PIs at different stages.