Current Collector Augmented Reductive Dissolution of Spent Li-Ion Battery Black Mass for Regeneration of NMC622 Cathode

Abstract Overcoming reliance on strong acid and external reductants in the hydrometallurgical recycling of spent lithium-ion batteries (LIBs) offers a promising pathway toward an environmentally benign and cost-effective strategy. In this study, we developed a current collector augmented reductive dissolution strategy using a mild phosphorus oxoacid as the hydrometallurgical leaching medium. The process utilizes aluminum current collector already present in the spent LIB black mass as an in situ reducing agent. Importantly, the proposed system addresses two key limitations of previously reported aluminum-assisted leaching processes, i.e., reliance on strongly acidic conditions and sluggish leaching kinetics, by operating under milder acidic conditions while exhibiting accelerated leaching kinetics. At optimized conditions, the process achieved maximum leaching efficiencies of approximately 94%, 89%, and 91% for Ni, Co, and Li, respectively. This reductive pathway lowered the leaching activation energy to below 13 kJ mol–1, indicating favorable dissolution kinetics. The transition metals are selectively retrieved as oxalates by means of chemical precipitation with more than 98% yield and subsequently used as precursors to synthesize LiNi0.6Mn0.2Co0.2O2 (rNMC). rNMC exhibits a well-ordered layered hexagonal structure with minimal cation mixing and successfully emulates the electrochemical performance of its commercial counterparts. During the initial galvanostatic cycle, rNMC demonstrated a discharge specific capacity of 131 mAh g–1 at 1C across an elevated potential window of 2.9–4.5 V, tested in a Li|rNMC half-cell. At 1C, the half-cell showed a remarkable capacity retention of 71% after 1000 cycles, indicating excellent electrochemical stability. This investigation demonstrates a mild and effective reductive dissolution pathway for the selective recovery of transition metals and repurposing them as LIB cathode active material. The proposed route is cost-effective and has potential for future scale-up.