Gaseous reduction of NMC-type cathode materials using hydrogen for metal recovery

Abstract

The ever-growing demand for rechargeable LIBs in portable electronic devices and electric vehicles has resulted in massive spent NMC-type batteries with the strong urge to recycle these batteries. Hydrogen reduction (pure and mixed gas (10 % H2 + 90% Ar)) of retrieved active cathode powder is investigated for the selective recovery of Li with Ni, Co, and Mn values. The research study was complimented with detailed characterization (XRD, SEM-EDS, XPS, and HRTEM) to analyze the processing mechanism. The thermodynamic evaluation followed by reduction experiments shows the NMC structure dissociation to metal/oxides above 400 °C. The magnetic fraction obtained from water-leached reduced mass possessed a saturation magnetization of 43 emu/g at 500 °C, 60 min containing MnO, Ni, Co, and Li2CO3 in the reduced powder (pure hydrogen) with 91 % Li recovery. Complete decomposition of the NMC structure was observed with 10 % hydrogen gas, but lower Li recovery was seen due to the formation of water-insoluble LiF. Lithium powder (Li2CO3 and LiOH mixture) of ∼0.19 kg and ∼0.62 kg of magnetic powder containing Co (15.2 %), Ni (38.1 %), and Mn (30.1 %) as MnO can be processed and is economical per kg of cathode powder.