Towards reagent use minimization in hydrometallurgical recycling of Li-NMC cathode materials via pH/ORP-controlled reductive leaching

Recycling of spent lithium-ion batteries via hydrometallurgy offers an effective alternative to pyrometallurgy for the recovery of Li, Ni, Co, and Mn, enabling full metal recovery at high purity. Nevertheless, hydrometallurgical recycling faces significant challenges, including high chemical reagent consumption and wastewater generation. Key targets for improvement are reducing excessive H 2 SO 4 and H 2 O 2 usage during leaching and consequently minimizing spent sodium sulfate (Na 2 SO 4 ) production. To address these issues, a pH/ORP-controlled double-feed leaching scheme was investigated and demonstrated in a semi-batch reactor configuration using virgin NMC 111 and NMC 622 cathode materials. By strictly controlling leaching conditions (pH = 1.5, ORP = 525 mV (vs. Ag/AgCl), T = 60 °C), near-complete metal extraction was achieved at 100 g/L solids loading, requiring only 26% excess H 2 SO 4 and 1.2% excess H 2 O 2 . Notably, Na 2 SO 4 production was reduced by 30% relative to uncontrolled leaching.