Acid-free metal leaching and facile active material delamination from LIB cathodes using supercritical CO2

초록

Supercritical CO2 (scCO(2)) was employed to address two crucial stages of lithium-ion battery (LIB) cathode recycling within a single experimental framework. A continuous scCO(2) stream with trace dimethyl sulfoxide or dimethylformamide removed poly(vinylidene fluoride) binder, detaching >95% of LiNi0.6Co0.2Mn0.2O2 (NCM622) and LiNi0.8Co0.15Al0.05O2 (NCA) coatings from Al-foil in <30 min at 353.15 K and 10 MPa. Unlike previous scCO(2)-assisted or hydrometallurgical methods using strong mineral acids, the metal recovery stage used acetylacetone (beta-diketone) with 4 vol% H2O2 at 313.15 K, 30 MPa, and a cosolvent-to-sample ratio of 5, achieving 80-90% Ni/Co/Mn extraction and similar to 60% Li recovery from NCM622. NCA showed similar Ni/Co recovery (similar to 80-85%) and 75% Al removal at identical conditions. Analyses suggest a diffusion-controlled shrinking-core mechanism for metal leaching. Avoiding strong acids, high heat, and large wastewater, this combined scCO(2) method offers an energy-efficient, environmentally friendly, and scalable closed-loop LIB recycling route.

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