Recycling of NMC black mass from spent lithium-ion battery using supercritical fluid extraction

The growing demand for lithium-ion battery recycling has intensified interest in selective and sustainable metal recovery techniques. In this study, we apply supercritical fluid extraction (SCFE) toreal industrial black mass, containing mixed-metal oxides along with typical impurities such as conductive carbon, binder residues, and metallic fragments. Unlike previous SCFE research focused on pure cathode powders, this work demonstrates the feasibility and selectivity of the process under practical impurity conditions. Usingsupercritical CO₂in combination with atributyl phosphate-nitric acid adductandhydrogen peroxideas a reducing agent, the process was optimized viafull factorial design and response surface methodology. Under optimal conditions (65 °C, 20.7  MPa, 5  mL/g adduct-to-solid ratio in units of mL adduct per gram of black mass, 8  mL (per 8 g of feed) hydrogen peroxide), extraction efficiencies exceeded90 % for Ni, Co, and Mn, whileLi recovery reached 73 %. Characterization byXRD, SEM-EDX, Raman spectroscopy, and TC/TOC analysisconfirmed metal removal and the structural persistence of carbonaceous material in the residue. Parametric tests highlighted the critical roles of the adduct and reducing agent in enabling efficient complexation and solubilization of transition metals. This work demonstrates that SCFE is a promising low-impact, chemically selective approach for lithium-ion battery recycling, capable of operating under mild conditions with reduced reagent consumption. It advances the feasibility of scalable, environmentally responsible recovery of critical materials from post-consumer batteries and sets the foundation for future integration with downstream purification or hybrid recycling technologies.