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.
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