An environmentally
friendly leaching process for recycling valuable
metals from spent lithium-ion batteries is developed. A sol–gel
method is utilized to resynthesize LiNi1/3Co1/3Mn1/3O2 from the leachate. Lactic acid is chosen
as a leaching and chelating agent. The leaching efficiency is investigated
by determining the contents of metal elements such as Li, Ni, Co,
and Mn in the leachate using inductively coupled plasma optical emission
spectroscopy. The spent cathode materials for the pretreatment process
and the regenerated and freshly synthesized materials are examined
using X-ray diffraction and scanning electronic microscopy. The results
show that the leaching efficiencies of Li, Ni, Co, and Mn reached
97.7, 98.2, 98.9, and 98.4%, respectively. The optimum conditions
are lactic acid concentration of 1.5 mol L–1, solid/liquid
ratio of 20 g L–1, leaching temperature of 70 °C,
H2O2 content of 0.5 vol %, and reaction time
of 20 min. The leaching kinetics of cathode scrap in lactic acid fit
well to the Avrami equation. Electrochemical analysis indicate that
the regenerated LiNi1/3Co1/3Mn1/3O2 cathode materials deliver a highly reversible discharge
capacity, 138.2 mA h g–1, at 0.5 C after 100 cycles,
with a capacity retention of 96%, comparable to those of freshly synthesized
LiNi1/3Co1/3Mn1/3O2 cathodes.
Rapid development of energy storage system causes a burst demand of lithium-ion batteries (LIBs), and large number of spent LIBs with high valuable metals are produced. Here we propose a novel application of oxalic acid leaching to regenerate Li(Ni 1/3 Co 1/3 Mn 1/3 )O 2 (NCM) cathodes from spent LIBs. With lithium dissolving into the solution, the transition metals transform into oxalate precipitates and deposit on the surface of spent NCM cathodes, separating lithium and transition metals in one simple step. After mixing with certain amount of Li 2 CO 3 , the oxalate precipitates together with unreacted NCM are directly calcined into new NCM cathodes. The regenerated NCM after 10 min leaching exhibits the best electrochemical performances, delivering the highest initial specific discharge capacity of 168 mA h g −1 at 0.2C and 153.7 mA h g −1 after 150 cycles with a high capacity retention of 91.5%. The excellent electrochemical performances are attributed to the submicrometer particles and voids after calcination, as well as the optimal proportion of elements. This process can make the most of valuable metals in the spent cathodes, with >98.5% Ni, Co, and Mn recycled. It is simple and effective, and provides a novel perspective of recycling cathodes from spent LIBs.
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