Investigation of Hydrogen Reduction of LiCoO<sub>2</sub> Cathode Material for the Recovery of Li and Co Values
Ganesh Shanker Bhandari, Nikhil Dhawan
Abstract
The massive availability of discarded LiCoO2 (LCO)-type batteries calls for inevitable metal recycling. Hydrogen reduction of retrieved cathode powder was investigated to recover Li and Co values selectively. A systematic experimental investigation with detailed characterization was conducted for the underlying reduction mechanism. Thermodynamic analysis and experimental evidence show that the stable layered LCO structure breaks to Co metal/oxides above 500 °C. The effect of temperature and time was studied, followed by water leaching for selective Li recovery. Magnetic separation was carried out on the leach residue, and 140 emu/g saturation magnetization of the magnetic fraction was found at 800 °C (60 min). A dissolution of 99% Co with 80% Li recovery was obtained at a lower reduction temperature (600 °C, 60 min) with a magnetic yield of 64%, followed by 2 M H2SO4 leaching. Reduction at a high temperature (800 °C) was beneficial for recovering metallic Co with a yield of 56% but with lower Li dissolution. HRTEM studies on reduced products reveal the complete reduction of the metallic Co phase and Li entrapment in the reduced powder. Overall, 52 g of lithium carbonate salt (Li2CO3 > 99%) and ∼380 g of a cobalt oxalate (>97%) precursor can be obtained from 1 kg of discarded batteries after hydrogen reduction at 600 °C. The proposed hydrogen reduction followed by magnetic separation is promising and sustainable for metal recovery from end-of-life batteries.